Electron Backscatter Diffraction (EBSD)

The goal of the study consolidated in this thesis is to understand the mechanics in steels using microscopy. In particular, the mechanical response of Transformation Induced Plasticity (TRIP) steels is correlated with their microstructures. Chapter 1 introduces the current state of the art of TRIP steels, highlighting the importance of microstructure - mechanical properties - applications relationships. In Chapter 2 the material properties and material processing are described into more detail, and an overview is presented of the characterization techniques used in this thesis. For the purpose of understanding the structure-property relationships, two TRIP steels (Al alloyed TRIP 700 and Si alloyed TRIP 800) and one TRIP assisted Multi Phase or TAMP (Nb microalloyed TAMP 800) steel were investigated in this study. The numbers (700, 800) designate the ultimate tensile strength of the materials. Despite the fact that steels are amongst the most extensively investigated materials, many features of the austenite-martensite transformation process during deformation remain unclarified to date.

Deformation induced transformation behavior of retained austenite grains is assessed in Chapter 3 with the help of Electron Back Scattered Diffraction (EBSD) and X-Ray Diffraction (XRD) techniques. The transformation tendency of retained austenite grains at the surface and inside the bulk as a result of uni-axial tension was investigated on TRIP 800 steel sheets. The experiments showed that the retained austenite grains at the surface have a stronger tendency to transform than the retained austenite grains in the bulk of the material. Local defects, such as twins, lower the stability of austenite grains and thus transform at the earlier stages of the deformation process. Austenite grains positioned at grain boundaries between multiple ferrite grains were amongst the first to transform, whereas austenite grains that are completely embedded in larger ferrite grains were often found to undergo rotations. These differences in strain-induced behavior are likely associated with different stress states and grain rotation capabilities of the austenite grains upon deformation. The rotation angles of embedded austenite grains were found to depend on the crystallographic orientation of the grains with respect to the straining direction. A lowering of Schmid factors of embedded austenite grains is seen to be the reason for the delayed transformation of these grains during the deformation process. The current findings suggest that grain rotation is an additional mechanism contributing to the high ductility of these steels and may be as important as the contribution of the austenite–martensite transformation. Furthermore, EBSD experiments were carried out on TRIP 700 steels which confirmed that the grain rotation behavior is consistent in both TRIP steels.

In addition to the austenite-to-martensite phase transformation, the role of alloying elements such as C, Mn, Si, and Al, and their effect on transformations during deformation, are poorly understood and there is an increasing need to gain fundamental insight into this topic. Consequently, in Chapter 4, a combination of Electron Back Scattered Diffraction (EBSD) and high-sensitivity Electron Probe Microanalysis (EPMA) was used to correlate the changes in microstructural features of metastable austenite grains upon deformation along with their respective local chemical compositions in TRIP 700 and TRIP 800 steels. In contrast to current metallurgical beliefs, we found direct evidence that austenite grains with higher Mn content transformed earlier than the grains with lower Mn contents. Various microstructural factors such as the local carbon concentrations, grain size, morphology, crystal lattice orientation in relation to strain direction, location of the grain in relation to its surrounding grains, and the presence of local defects (twins) were investigated. Analysis performed on several twinned austenite grains showed higher enrichment of Mn contents and an early transformation during deformation. At a very local scale, the austenite grains with high Mn contents have an inhomogeneous Mn distribution which can result in local strain acting as a trigger for early transformation. The local variation in manganese content therefore allows for an overall gradual transformation of the retained austenite grains, providing another tunable parameter for deformation induced austenite-to-martensite transformation.

Multiphase steels designed with composite strengthening may be further strengthened by grain refinement or precipitation by the addition of microalloying elements. In Chapter 5 we have therefore investigated microstructures and precipitates in a Nb microalloyed TRIP assissted multiphase (TAMP) steel containing ferrite, bainite, martensite and retained austenite. Precipitates were observed in the ferrite, martensite and bainite phases, but not in the austenite phase. Two kinds of precipitates were found in this steel: NbC and novel (Nb,Ti)N phases. The (Nb,Ti)N precipitates were found in different sizes, ranging from 10-150 nm, whereby the larger precipitates have a Ti/Nb atomic ratio of approximately 2.83 - 0.81 and were faceted in shape. Smaller NbC precipitates were found in a size range of 5-20 nm. The (Nb,Ti)N precipitates have a well-defined Nishiyama Wasserman (N-W) orientation relationship with the ferrite matrix, while the NbC precipitates have random orientations. Both NbC and (Nb,Ti)N carbide precipitates are expected to take part in strengthening of these steels. The comparison of calculated lattice parameters and experimental lattice parameters indicates that both precipitates are deficient in carbon and nitrogen contents.

In Chapter 6 the investigations on nano-sized precipitates in Al alloyed TRIP 700 steel with Ti micro additions are described. Two types of Ti(N) precipitates were observed with cubic and faceted morphologies. The faceted precipitates were found in a size range of 40-70 nm and the cubic precipitates in a size range of 70-120 nm. The cubic precipitates had higher nitrogen concentrations and exhibited slightly larger lattice parameters than the faceted TiN precipitates. Additionally, spherical shaped Ti2CS precipitates were found with sizes ranging from 20 to 100 nm. Both the cubic and faceted Ti(N) precipitates and Ti2CS precipitates were found in random orientations with respect to the ferrite matrix. A novel iron carbide precipitate was observed in all ferrite grains. These Fe(C) precipitates have sizes ranging from 2 to 5 nm and exhibited disc-shaped morphologies. All the Fe(C) precipitates showed a well-defined Pitsch Schrader (P-S) orientation relationship with the ferrite matrix. From the precipitate size, inter-particle spacing, and lattice misfit calculations, the newly observed Fe(C) precipitates are considered to possess significant potential in enhancing the strength of these steels. Electron microscopy experiments were also carried out on Si alloyed TRIP 800 steels which confirmed that ultrafine Fe(C) precipitates exist in both TRIP counterparts.

The elements Chromium (Cr) and Manganese (Mn) are well known in technologically important iron and steel alloys. In Chapter 7 it is revealed for the first time that Cr and Mn have combined to form two novel ternary carbides. These novel ternary carbide phases were identified in TRIP-assisted multi phase (TAMP) steel. The carbides were characterized using transmission electron microscopy (TEM), electron diffraction and density functional theory (DFT) calculations. Electron diffraction analysis revealed that the Orthorhombic carbide has lattice parameters a = 5.09 Å, b = 6.98 Å, and c = 4.55 Å, with a Pnma space group, while the Monoclinic carbide has lattice parameters a = 6.83 Å, b = 4.54 Å, c = 5.00 Å, and β = 92.2° with a P21/c space group. Excellent agreement was found between calculation and experiment on the lattice parameters and relative atomic positions. Remarkable Mn-Cr alloying leads to these ternary phases having high thermodynamic stabilities. The calculations have shown that introduction of carbon atoms strongly induce magnetism within these structures and that these carbides are stable also at higher pressures.

This paper provides a brief overview of a multidisciplinary effort at the Naval Research Laboratory aimed at developing a computationally-based methodology to assist in the design of advanced Naval steels. This program uses multiple computational techniques ranging from the atomistic length scale to continuum response. First-principles electronic structure calculations using density functional theory were employed, semi-empirical angular dependent potentials were developed based on the embedded atom method, and these potentials were used as input into Monte-Carlo and molecular dynamics simulations. Experimental techniques have also been applied to a super-austenitic stainless steel (AL6XN) to provide experimental input, guidance, verification, and enhancements to the models. These experimental methods include optical microscopy, scanning electron microscopy, transmission electron microscopy, electron backscatter diffraction, and serial sectioning in conjunction with computer-based three-dimensional reconstruction and quantitative analyses. The experimental results are also used as critical input into mesoscale finite element models of materials response.

Strain induced grain refinement of an Al-1 wt.%Mg alloy processed by equal channel angular pressing (ECAP) at cryogenic temperature is investigated quantitatively. The results show that both mean grain and subgrain sizes are reduced gradually with increasing ECAP pass. ECAP at cryogenic temperature increases the rate of grain refinement by promoting the fraction of high angle grain boundaries (HAGBs) and misorientation at each pass. The fraction of HAGBs and the misorientation of Al-1 wt.% Mg alloy during ECAP at cryogenic temperature increase continuously as a function of equivalent strain. Both {110} and {111} twins at ultrafine-grained size are observed firstly in Al-Mg alloy during ECAP. The analysis of grain boundaries and misorientation gradients demonstrates the grain refinement mechanism of continuous dynamic recrystallization.

Multi-proxy approach was used to reconstruct the environmental conditions of remote lakes in the High Tatra Mountains (Slovakia) over the past few centuries (approximately 500-1000 years). Short sediment cores (*30 cm) taken from three morphologically similar glacial lakes distributed along altitudinal gradient (subalpine to alpine conditions) were analysed for organic matter content (LOI), diatoms and chironomids. Both descriptive and correlative approaches were used for analysing stratigraphical data. Predictive canonical correspondence analysis and co-correspondence analysis were applied to directly relate physical and biological proxies to each other. The relationship between LOI and biotic proxies was inconsistent across groups and lakes. Concordant patterns in diatom and chironomid composition were found in two non-acidified lakes. Common trends in those assemblages indicated major past environmental events such as the Little Ice Age, air pollution and lake acidification. In contrast, no relationship between the composition of diatom and chironomid assemblages was found in the formerly acidified lake, suggesting different responses of assemblages to acidification. While chironomids showed shifts that are attributable to recovery, diatoms assemblage remained relatively stable throughout the uppermost layers of the sediment record. On the other hand, climatic-driven changes in assemblages detected in the deeper layers were more pronounced in diatoms than in chironomids.

Suppose that a random process Z(s; t), indexed in space and time, has a spatio-temporal stationary covariance C(h; u), where h 2 IR d (d 1) is a spatial lag and u 2 IR is a temporal lag. Separable spatio-temporal covariances have the property that they can be written as a product of a purely spatial covariance and a purely temporal covariance. Their ease of de nition is counterbalanced by the rather limited class of random processes to which they correspond. In this article, we derive a new approach that allows one to obtain many classes of nonseparable, spatio-temporal stationary covariance functions and we t several such to spatio-temporal data on wind speed over a region in the tropical western Paci c ocean.

however, subtle processes which involve the specimen, the however, subtle processes which involve the specimen, the electron beam and any mobile species on the sample electron beam and any mobile species on the sample surface frequently cause the build up of hydrocarbon surface frequently cause the build up of hydrocarbon contamination layers. contamination layers.

TRIP-assisted steels are ideal for lightweight automotive applications due to their high strength and ductility. The selective oxidation of the alloying elements Mn, Al and Si during annealing prior to galvanizing can cause poor reactive wetting during galvanizing, resulting in bare spot defects. Despite the selective oxidation of alloying elements two high Al-low Si TRIP steels were successfully galvanized. It was determined that good reactive wetting occurred by the presence of an Al-rich interfacial layer composed of Fe 2 Al 5 and FeAl 3 . Two mechanisms by which reactive wetting occurred were identified; (1) aluminothermic reduction of MnO by the Al in the Zn bath and (2) Zn bridging of oxide particles. When aluminothermic reduction occurred there was a localized depletion of Al in the Zn bath resulting in inhibition breakdown and the formation of Fe-Zn intermetallics at the Fe-Zn interface.

Surface quality development on series of metal samples was investigated using a new Ar ion milling apparatus. The surface quality of samples was characterized by the image quality (IQ) parameter of the electron backscatter diffraction (EBSD) measurement. Ar ion polishing recipes have provided to prepare a surface appropriate for high quality EBSD mapping. The initial surfaces of samples were roughly grinded and polished. High quality surface smoothness could be achieved during the subsequent Ar ion polishing treatment. The optimal angles of Ar ion incidence and the polishing times were determined for several materials.

Ferritic–martensitic dual phase (DP) steels deform spatially in a highly heterogeneous manner, i.e. with strong strain and stress partitioning at the micro-scale. Such heterogeneity in local strain evolution leads in turn to a spatially heterogeneous damage distribution, and thus, plays an important role in the process of damage inheritance and fracture. To understand and improve DP steels, it is important to identify connections between the observed strain and damage heterogeneity and the underlying microstructural parameters, e.g. ferrite grain size, martensite distribution, martensite fraction, etc. In this work we pursue this aim by conducting in-situ deformation experiments on two different DP steel grades, employing two different microscopic-digital image correlation (lDIC) techniques to achieve microstructural strain maps of representative statistics and high-resolution. The resulting local strain maps are analyzed in connection to the observed damage incidents (identified by image post-processing) and to local stress maps (obtained from crystal plasticity (CP) simulations of the same microstructural area). The results reveal that plasticity is typically initiated within ‘‘hot zones’’ with larger ferritic grains and lower local martensite fraction. With increasing global deformation, damage incidents are most often observed in the boundary of such highly plastified zones. High-resolution lDIC and the corresponding CP simulations reveal the importance of martensite dispersion: zones with bulky martensite are more susceptible to macroscopic localization before the full strain hardening capacity of the material is consumed. Overall, the presented joint analysis establishes an integrated computational materials engineering (ICME) approach for designing advanced DP steels.

The influence of direct quenching (DQ) on microstructure and mechanical properties of 0.19C-1.7Si-1.0 Mn-0.05Nb steel was studied. The microstructure and mechanical properties of reheat quenched and tempered (RQ&T) steel plate were compared with those of direct quenched and tempered (DQ&T) steel plates which were hot rolled at different finish rolling temperatures (1173 K and 1123 K), i.e., recrystallization-controlled-rolled direct-quenched (RCR&DQ) and controlled-rolled direct-quenched (CR&DQ), respectively. The strengths generally increased in the following order: RQ&T<RCR&DQ&T< CR&DQ&T. Strength differences between the CR&DQ&T and RQ&T conditions as high as 14% were observed at the tempered temperature of 573 K. The optical microscopy of the CR&DQ&T steel showed deformed grains elongated along the rolling direction, while complete equiaxed grains were visible in RQ&T and RCR&DQ&T steels. Transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD) of the DQ steels showed smaller block width and higher density of dislocations. Inheritance of austenite deformation substructure by the martensite and differences in martensite block width were ruled out as major causes for the strength differences between DQ and RQ steels.

During low-temperature faulting of Cambrian quartzite (Assynt, NW Scotland), stress concentrations develop at grain contacts either at the onset of deformation, prior to the establishment of a through-going fault plane, or within the damage zone remote from the main displacement segment. Such concentrations contribute to the development of intragranular microfractures, cataclastic microstructures and fault rocks. This contribution considers the progressive deformation sequence that precedes microfracturing and cataclasis. The complexity of this deformation is revealed by scanning electron microscope (SEM) electron backscattered diffraction (EBSD). Dauphine  twinning is a widespread feature associated with grain contact stress concentration and forms distinctive EBSD microstructures. Automatic SEM/EBSD analysis reveals that whilst initial indentation causes dauphine  twinning of many grains, continued indentation results in the formation of an arcuate array of subgrains via low temperature plasticity and/or microcracking, which overprint the dauphine  twins. These observations are consistent with transmission electron microscopic analysis of quartz crystals used for microhardness indentation tests, which reveal that indentation causes an intensely deformed region to develop, comprising a high density of microfractures and a submicron scale`blocky' microstructure that accommodates any`plastic' deformation. Deformation mechanisms and associated microstructures develop sequentially with progressive indentation and may provide sites of microfracture nucleation via low-temperature ductile fracture. The new microstructures assist diffusive mass transfer (DMT) processes by the formation of a cellular or subgrain array that represents a reduction of several orders of magnitude in apparent grain size and hence in diffusion path length. Concomitantly, associated microfracturing perturbs local thermodynamic equilibrium, leading to enhanced DMT, crack healing and cementation overgrowths. Together, these processes form the aseismic creep and sealing components of fault zone development. Published by Elsevier Science Ltd.

Laser diodes (LD) are usually bonded onto heat sinks for the purposes of heat dissipation, mechanical support and electrical interconnect. In this study, energy dispersive X-ray analysis (EDX) and electron backscatter diffraction (EBSD) are employed to investigate the microstructure evolution of 80Au/20Sn solder joint in LD package. During reflow, Pt-Sn and (Au, Ni)Sn IMCs were formed at the respective LD/solder and solder/heatsink interfaces, while d, b and f 0 phases of Au/Sn intermetallics were found in the solder joint. The Au-rich b and f 0 phases in the solder joint limit the growth of interfacial IMCs. Chip shear testing showed that the failure occurred within the LD, with partial brittle fracture at the GaAs substrate and partial interfacial delamination at the GaAs/SiN interface. The strong solder bond can be attributed to the high mechanical strength of 80Au/20Sn solder, which provides improved stability for high temperature applications.

Hydrogen embrittlement in 304L austenitic stainless steel fabricated by laser powder-bed-fusion (LPBF) was investigated and compared to conventionally produced 304L samples with two different processing histories; casting plus annealing (CA) and CA plus thermomechanical treatment (CA-TMT). Interestingly, no significant difference in the amount of deformation-induced α ′ martensite between the LPBF and CA-TMT samples was observed, suggesting that the solidification substructure in the LPBF sample enhanced the strength without promoting the harmful hydrogen embrittlement effect. These results are discussed in terms of the chemical in-homogeneity, hydrogen-assisted cracking behavior, and hydrogen diffusion and trapping in the present 304L samples.

The microstructures of two contrasting garnet grains are mapped using automated electron backscatter diffraction. In both cases there is a very strong crystallographic preferred orientation, with measurements clustered round a single dominant orientation. Each garnet grain is divided into domains with similar orientations, limited by boundaries with misorientations of 28 or more. In both samples most of misorientation angles measured across orientation domain boundaries are signi®cantly lower than those measured between random pairs of orientation domains. One sample is a deformed garnet that shows considerable distortion within the domains. Lines of orientation measurements within domains and across domain boundaries show small circle dispersions around rational crystallographic axes. The domain boundaries are likely to be subgrain boundaries formed by dislocation creep and recovery. The second sample is a porphyroblast in which the domains have no internal distortion and the orientation domain boundaries have random misorientation axes. These boundaries probably formed by coalescence of originally separate garnets. We suggest that misorientations across these boundaries were reduced by physical relative rotations driven by boundary energy. The data illustrate the potential of orientation maps and misorientation analysis in microstructural studies of any crystalline material. q

A method for decorating the surface of disk electrodes with metal nanowires is presented. Cu and Ni nanowires with diameters from 1.0 μm to 0.2 μm are directly deposited on the electrode surface using a polycarbonate membrane filter template maintained in contact with the metal substrate by the soft homogeneous pressure of a sponge soaked with electrolyte. The morphologic and structural properties of the deposit are characterized by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The latter shows that the head of nanowires with diameter of 0.4 μm is ordinarily polycrystalline, and that of nanowires with diameter of 0.2 μm is almost always monocrystalline for Cu and frequently also for Ni. Cyclic voltammetries and impedance investigations recorded in alkaline solutions at representative Ni electrodes decorated with nanowires provide consistent values of roughness factor, in the range 20–25.

Multi-proxy approach was used to reconstruct the environmental conditions of remote lakes in the High Tatra Mountains (Slovakia) over the past few centuries (approximately 500-1000 years). Short sediment cores (*30 cm) taken from three morphologically similar glacial lakes distributed along altitudinal gradient (subalpine to alpine conditions) were analysed for organic matter content (LOI), diatoms and chironomids. Both descriptive and correlative approaches were used for analysing stratigraphical data. Predictive canonical correspondence analysis and co-correspondence analysis were applied to directly relate physical and biological proxies to each other. The relationship between LOI and biotic proxies was inconsistent across groups and lakes. Concordant patterns in diatom and chironomid composition were found in two non-acidified lakes. Common trends in those assemblages indicated major past environmental events such as the Little Ice Age, air pollution and lake acidification. In contrast, no relationship between the composition of diatom and chironomid assemblages was found in the formerly acidified lake, suggesting different responses of assemblages to acidification. While chironomids showed shifts that are attributable to recovery, diatoms assemblage remained relatively stable throughout the uppermost layers of the sediment record. On the other hand, climatic-driven changes in assemblages detected in the deeper layers were more pronounced in diatoms than in chironomids.

Deformation behavior and texture evolution of the material can be significantly affected by strain path change. For this reason, two rolling methods, unidirectional rolling (UR) and clock rolling (CR), were employed to manufacture tantalum plates. Texture evolution during unidirectional rolling and clock rolling was studied respectively by orientation distribution function (ODF). Related annealed microstructures were investigated by orientation image map (OIM). Usually, unidirectional rolling led to a strengthening of the main texture component with increasing strain, but for tantalum dominant texture component {0 0 1} -fiber was stable after 70% deformation, while minor texture component {1 1 1} ␥fiber was enhanced with increasing strain. In clock rolling, both of the two fibers were not stable any more for their intensity varied with rolling pass. After the final deformation, a similar texture was produced by the two rolling methods. However, recrystallization texture revealed a big difference. Such different texture development was contributed to microstructural change resulted from rolling path change.

We introduce a new class of high-entropy alloys (HEAs), i.e., quinary (five-component) dual-phase (DP) HEAs revealing transformation-induced plasticity (TRIP), designed by using a quantum mechanically based and experimentally validated approach. Ab initio simulations of thermodynamic phase stabilities of Co 20 Cr 20 Fe 40-x Mn 20 Ni x (x ¼ 0e20 at. %) HEAs were performed to screen for promising compositions showing the TRIP-DP effect. The theoretical predictions reveal several promising alloys, which have been cast and systematically characterized with respect to their room temperature phase constituents, microstructures, element distributions and compositional homogeneity, tensile properties and deformation mechanisms. The study demonstrates the strength of ab initio calculations to predict the behavior of multi-component HEAs on the macroscopic scale from the atomistic level. As a prototype example a non-equiatomic Co 20 Cr 20 Fe 34 Mn 20 Ni 6 HEA, selected based on our ab initio simulations, reveals the TRIP-DP effect and hence exhibits higher tensile strength and strain-hardening ability compared to the corresponding equiatomic CoCrFeMnNi alloy.

A laser beam welding process via heat conduction was applied to join DC01 steel with aluminum (Al)in overlap configuration without filler wire. The effect of the applied laser power (1.7, 1.8, 2.1, and2.4kW) on the formation and evolution of the interfaces between steel and Al was analyzed. Twointermetallic compounds were found at the interface, namely, one adjacent to the steel layer (Al
5
Fe
2
)and one close to the solidified Al (Al
13
Fe
4
). The thickness of the intermetallic reaction layer increaseswith laser power, while the morphology of its individual components evolves due to differences inaccumulated thermal cycles. Correlations between simulations and measurements show that the peaktemperature has significantly stronger influence on the thickness of the intermetallic reaction layerthan cooling time and the integral of temperature over the time. Shear/tensile strength tests reveal thatall the specimens fail in the Al heat affected zone

Firewalls provide a variety of services to networks in terms of security. They provide for network address tr networks (VPN), and filtering of traffic that does not conform to the network's stated security policy. There simple packet filters to circuit-level gateways to proxy firewalls. Firewalls are being asked to fill a larger and security these days than several years ago. One of the more recent innovations in firewall technology is the inspection or DPI. Deep Packet Inspection can be seen as the integration of Intrusion Detection (IDS) and I capabilities with traditional stateful firewall technology. Traditional networks have a defined boundary dema

Image quality~IQ! maps constructed from electron backscatter diffraction data provide useful visualizations of microstructure. The contrast in these maps arises from a variety of sources, including phase, strain, topography, and grain boundaries. IQ maps constructed using various IQ metrics are compared to identify the most prominent contrast mechanism for each metric. The conventional IQ metric was found to provide the superior grain boundary and strain contrast, whereas an IQ metric based on the average overall intensity of the diffraction patterns was found to provide better topological and phase contrast.

Depending on the strain and temperature regime examined recovery of bcc metals during hot rolling or annealingsubsequent to cold deformation often leads to the preservation of certain deformation texture components. A broad variety of mesoscopic and macroscopic texture datafrom both hot rolled and cold rolled and annealed bcc metals (Fe, Ta, Mo, Nb) and alloys (low-carbon steels, ferritic stainless steels, transformer steels) is re-examined with respect to such phenomena.

The purpose of this exploratory study is to better understand the current dynamics of the Malaysian market for smartphone and the usage behaviors of consumers. This paper presents the result of a survey on the trend of smartphone from the perspective of end consumers. The data was collected from 1814 respondents across major cities in Malaysia. This study has looked into the familiarity of users towards smartphones, choices of smartphone brand and service providers, and most importantly the determinants that influence their purchasing decision. Additionally, the consumers' preferences on smartphone specifications such as design, computing power, operating platform, and price were investigated. Furthermore, consumers' usage behaviors such as using smartphone for email, web browsing, gaming, and document reading were examined. The statistics presented provides fundamental information regarding the trends in the smartphone market and usage behaviors in Malaysia. Such information are useful for academics for the development of future works in the field, whereas for smartphone manufacturers, application developers and other stakeholders, they are able to plan their direction in the Malaysian smartphone market.

One hundred and thirty-five degree clock rolling significantly improves the texture
homogeneity of tantalum sheets along the thickness, but a distinctly fragmented substructure isformed within {111} (<111>//normal direction (ND)) and {100} (<100>//ND) deformation grains,which is not suitable to obtain a uniform recrystallization microstructure. Thus, effects of differentannealing temperatures on the microstructure and texture heterogeneity of tantalum sheets along thethickness were investigated by X-ray diffraction (XRD), electron backscatter diffraction (EBSD) andtransmission electron microscopy (TEM). Results show that the texture distribution along -fiber and-fiber is irregular and many large grains with {111} orientation develop during annealing at hightemperature. However, low-temperature annealing can not only weaken the texture intensity in thesurface and the center layer but also introduce a more uniform grain size distribution. This result can
be attributed to the subgrain-nucleation-dominated recrystallization mechanism induced by recoveryat low temperature, and moreover, a considerable decline of recrystallization driving force resultingfrom the release of stored energy in the deformation matrix.

Deformation-induced martensitic transformation (DIMT) has been
used for designing high-performance alloys to prevent structural
failure under static loads. Its effectiveness against fatigue, however,
is unclear. This limits the application of DIMT for parts that
are exposed to variable loads, although such scenarios are the rule
and not the exception for structural failure. Here we reveal the
dual role of DIMT in fatigue crack growth through in situ observations.
Two antagonistic fatigue mechanisms mediated by DIMT are
identified, namely, transformation-mediated crack arresting,
which prevents crack growth, and transformation-mediated crack
coalescence, which promotes crack growth. Both mechanisms are
due to the hardness and brittleness of martensite as a transformation
product, rather than to the actual transformation process
itself. In fatigue crack growth, the prevalence of one mechanism
over the other critically depends on the crack size and the mechanical
stability of the parent austenite phase. Elucidating the two
mechanisms and their interplay allows for the microstructure
design and safe use of metastable alloys that experience fatigue
loads. The findings also generally reveal how metastable alloy
microstructures must be designed for materials to be fatigueresistant.

Austenitic stainless steels are widely used in high performance pressure vessels, nuclear, chemical, process and medical industry due to their very good corrosion resistance and superior mechanical properties. However, austenitic stainless steels are prone to sensitization when subjected to higher temperatures (673 K to 1173 K) during the manufacturing process (e.g. welding) and/or certain applications (e.g. pressure vessels).

ISBN 958-9262-17-1 © Elcy Corrales Roa 2 CONTENIDO INTRODUCCIÓN EL PUNTO DE PARTIDA 1. GUÍA CONCEPTUAL Para moverse en la sostenibilidad • Conceptos relacionados • ¿Pueden ir juntos? 2. LA LENTE DE LA SOSTENIBILIDAD • Utilización de los recursos . naturales renovables • Uso de tecnologías inadecuadas • Recursos externos e internos: balance 3. ALGUNAS SEÑALES PARA UN AGRO SOSTENIBLE • Tradición y sostenibilidad • Contribución a la producción sostenible 4. EXPERIENCIAS, ACTORES, LUGARES Y MÈTODOS Campesinos y sostenibilidad • Información y fuentes de información • Tipos de organización y experiencias • Metodologías de trabajo 5. Cipav y el desarrollo sostenible UN EJEMPLO DE INVESTIGACIÓN 6. RESULTADOS Y ESCALAS DE APLICACIÓN • Resultados que ilustran • Escalas de aplicación • De una escala a otra • La perspectiva 7. PRODUCCIÓN CAMPESINA Y SOSTENIBILIDAD Resumen y conclusiones • Reconocimiento • Alcances y debilidades • Localización 3 • Inversión e investigación • Las redes • El lugar del campesinado • Ordenamiento territorial 4

Dual-phase (DP) steel is the flagship of advanced high-strength steels, which were the first among various candidate alloy systems to find application in weight-reduced automotive components. On the one hand, this is a metallurgical success story: Lean alloying and simple thermomechanical treatment
enable use of less material to accomplish more performance while complying with demanding environmental and economic constraints. On the other hand, the enormous literature onDP steels demonstrates the immense complexity ofmicrostructure physics inmultiphase alloys: Roughly 50 years after the first reports on ferrite-martensite steels, there are still various open scientific questions. Fortunately, the last decades witnessed enormous advances in the development of enabling experimental and simulation techniques, significantly improving the understanding of DP steels. This review provides
a detailed account of these improvements, focusing specifically on (a) microstructure evolution during processing, (b) experimental characterization of micromechanical behavior, and (c) the simulation of mechanical behavior, to highlight the critical unresolved issues and to guide future research efforts.

This is a study on grain-scale micromechanics of polycrystal surfaces during plastic straining. We use Al–Mg–Si sheets (alloy AA6022) as model material. The work aims at understanding the relationship between microstrain heterogeneity and surface roughness in plastically strained polycrystals in terms of the surface and through-thickness microstructure. Experiments were conducted on polycrystals with identical composition but different processing and microstructures. We performed tensile and bending tests on sheet samples cut in transverse and rolling directions. We investigated the plastic surface microstrains (photogrametry), surface topography (confocal microscopy), particle distribution (metallography, SEM), microtexture (EBSD), and grain size distribution (EBSD) in the same sample regions.
We also conducted in-situ straining experiments where the microtexture, surface topography, and stress–strain behavior
were simultaneously determined. The results reveal a relationship between the heterogeneity of plastic surface microstrains, roughness, and microstructure. In particular a correlation could be established between microstrains and banded microtexture components (Cube, Goss, {111}[uvw]).

"A new work-hardening model for homogeneous and heterogeneous cell-forming alloys is introduced. It distinguishes three internal state variables in terms of three categories of dislocations: mobile dislocations, immobile dislocations in the cell interiors and immobile dislocations in the cell walls. For each
dislocation population an evolution law is derived taking into account dislocation generation, annihilation and storage by dipole and lock formation. In particular, these rate equations take into account the number of active glide systems and, thus, introduce texture in the model in addition to the Taylor factor. Microstructure is represented by the dislocation cell structure as well as second-phase particles, which may undergo changes
by precipitation and Ostwald ripening. Interaction of mobile dislocations with the microstructure is taken into account through an effective slip length of the mobile dislocations. For the same set of parameters, the predictions are in excellent agreement with measured stress–strain curves of both a precipitation-hardened aluminium alloy (Al–4.16 wt% Cu–1.37 wt% Mg, AlCuMg2) and a precipitation-free model alloy (Al–0.35 wt% Cu–0.25 wt% Mg), the composition of which corresponds to the matrix of the two-phase alloy."

Two plain carbon steels with varying manganese content (0.87 wt pct and 1.63 wt pct) were refined to approximately 1 μm by large strain warm deformation and subsequently subjected to intercritical annealing to produce an ultrafine grained ferrite/martensite dual-phase steel. The influence of the Mn content on microstructure evolution is studied by scanning electron microscopy (SEM).

We study orientation gradients and geometrically necessary dislocations (GNDs) in two ultrafine grained dual-phase steels with different martensite particle size and volume fraction (24 vol.% and 38 vol.%). The steel with higher martensite fraction has a lower elastic limit, a higher yield strength and a higher tensile strength. These effects are attributed to the higher second phase fraction and the inhomogeneous transformation strain accommodation in ferrite. The latter assumption is analyzed using high-resolution electron backscatter diffraction (EBSD). We quantify orientation gradients, pattern quality and GND density variations at ferrite–ferrite and ferrite–martensite interfaces. Using 3D EBSD, additional information is obtained about the effect of grain volume and of martensite distribution on strain accommodation. Two methods are demonstrated to calculate the GND density from the EBSD data based on the kernel average misorientation measure and on the dislocation density tensor, respectively. The overall GND density is shown to increase with increasing total martensite fraction, decreasing grain volume, and increasing martensite fraction in the vicinity of ferrite.

Medium Mn steels possess a composite like microstructure containing multiple phase constituents like metastable austenite, ferrite, d-ferrite and a0-martensite with a wide range of fractions for each constituent. The high mechanical contrast among them and the deformation-driven evolution of the microstructure lead to complex fracture mechanisms. Here we investigate tensile fracture mechanisms of medium Mn steels with two typical types of microstructures.

The recently developed interstitial high-entropy alloys (iHEAs) exhibit an enhanced combination of strength and ductility. These properties are attributed to dislocation hardening, deformation-driven athermal phase transformation from the face-centered cubic (FCC) g matrix into the hexagonal close-packed (HCP) ε phase, stacking fault formation, mechanical twinning and precipitation hardening. For gaining a better understanding of these mechanisms as well as their interactions direct observation of the deformation process is required. For this purpose, an iHEA with nominal composition of Fe-30Mn-10Co-10Cr-0.5C (at. %) was produced and investigated via in-situ and interrupted in-situ tensile testing in a scanning electron microscope (SEM) combining electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD) techniques. The results reveal that the iHEA is deformed by formation and multiplication of stacking faults along {111} microbands. Sufficient overlap of stacking faults within microbands leads to intrinsic nucleation of HCP ε phase and incoherent annealing twin boundaries act as preferential extrinsic nucleation sites for HCP ε formation. With further straining HCP ε nuclei grow into the adjacent deformed FCC g matrix. g regions with smaller grain size have higher mechanical stability against phase transformation. Twinning in FCC g grains with a size of ~10 mm can be activated at room temperature at a stress below ~736 MPa. With increasing deformation, new twin lamellae continuously nucleate. The twin lamellae grow in preferred directions driven by the motion of the mobile partial dislocations. Owing to the individual grain size dependence of the activation of the dislocation-mediated plasticity, of the athermal phase transformation and of mechanical twinning at the different deformation stages, desired strain hardening profiles can be tuned and adjusted over the entire deformation regime by adequate microstructure design, providing excellent combinations of strength and ductility.

The effect of Mn content on the microstructure and mechanical properties of two ultrafine grained0.2%C–Mn steels has been investigated. The ultrafine grained microstructure was produced by use of largestrain warm deformation and subsequent annealing. The final microstructure consists of fine cementite par-ticles within an ultrafine grained ferrite matrix. The increase in the Mn content leads to a decrease in the average ferrite grain size (from 1.3 to 0.8 um for an increase in the Mn content from 0.74 to  1.52mass%). This can be attributed to the enrichment of Mn in the cementite particles, which becomes finer in the steelwith a higher Mn content. The increase in the Mn content results in an increase in strength at equal ductility and toughness.

Three ferrite/martensite dual-phase steels varying in the ferrite grain size (12.4, 2.4 and 1.2 um) but with the same martensite content (30 vol.%) were produced by large-strain warm deformation at different deformation temperatures, followed by intercritical annealing. Their mechanical properties were compared, and the response of the ultrafine-grained steel (1.2 um) to aging at 170 °C was investigated. The deformation and fracture mechanisms were studied based on microstructure observations using scanning electron microscopy and electron backscatter diffraction. Grain refinement leads to an increase in both yield strength and tensile strength, whereas uniform elongation and total elongation are less affected. This can be partly explained by the increase in the initial strain-hardening rate. Moreover, the stress/strain partitioning characteristics between ferrite and martensite change due to grain refinement, leading to enhanced martensite plasticity and better interface cohesion. Grain refinement further promotes ductile fracture mechanisms, which is a result of the improved fracture toughness of martensite. The aging treatment leads to a strong increase in yield strength and improves the uniform and total elongation. These effects are attributed to dislocation locking due to the formation of Cottrell atmospheres and relaxation of internal stresses, as well as to the reduction in the interstitial carbon content in ferrite and tempering effects in martensite.

In the present work, we report our recent progress in the development, optimization, and application of a technique for the three-dimensional (3-D) high-resolution characterization of crystalline microstructures. The technique is based on automated serial sectioning using a focused ion beam (FIB) and characterization of the sections by orientation microscopy based on electron backscatter diffraction (EBSD) in a combined FIB-scanning electron microscope (SEM). On our system, consisting of a Zeiss-Crossbeam FIB-SEM and an EDAX-TSL EBSD system, the technique currently reaches a spatial resolution of 100 · 100 · 100 nm 3 as a standard, but a resolution of 50 · 50 · 50 nm 3 seems to be a realistic optimum. The maximum observable volume is on the order of 50 · 50 · 50 lm 3 . The technique extends all the powerful features of two-dimensional (2-D) EBSD-based orientation microscopy into the third dimension of space. This allows new parameters of the microstructure to be obtained-for example, the full crystallographic characterization of all kinds of interfaces, including the morphology and the crystallographic indices of the interface planes. The technique is illustrated by four examples, including the characterization of pearlite colonies in a carbon steel, of twins in pseudonanocrystalline NiCo thin films, the description of deformation patterns formed under nanoindents in copper single crystals, and the characterization of fatigue cracks in an aluminum alloy. In view of these examples, we discuss the possibilities and limits of the technique. Furthermore, we give an extensive overview of parallel developments of 3-D orientation microscopy (with a focus on the EBSD-based techniques) in other groups.

In dual-phase (DP) steels, inherited microstructures and elemental distributions affect the kinetics and morphology of phase transformation phenomena and the mechanical properties of the final material. In order to study the inheritance process, we selected two model materials with the same average DP steel composition but with different initial microstructures, created by coiling at different temperatures
after hot rolling. These samples were submitted to a DP-steel heat treatment consisting of a short isothermal annealing in the pure austenite region and a quenching process. The evolution of microstructure, chemical composition and mechanical properties (hardness) during this treatment was investigated.
The initial samples had a bainitic–martensitic (B + M) microstructure for the material coiled at lower temperature and a ferritic–pearlitic (P + F) microstructure for that coiled at higher temperature. The P + F microstructure had a much more inhomogeneous distribution of substitutional elements (in particular of Mn) and of carbon. After complete heat treatment, both materials showed a typical DP microstructure (martensite islands embedded in ferrite) but the P + F material showed lower hardness compared to the B + M material. It was found that the inhomogeneous elemental distribution prevailed in the P + F material.
The inheritance process was studied by combining  measurements of the elemental distribution by Wavelength-Dispersive X-ray spectroscopy (WDX), simulations of the evolution of the elemental composition via the DICTRA (diffusion-controlled reactions) computer programme, dilatometry to observe the kinetics of phase transformation, and observation and quantification of the microstructures by
Electron Backscatter Diffraction (EBSD) measurements. For the P + F material it was found that the a–c transformation during annealing is slowed down in regions of lower Mn content and is therefore not completed. During the subsequent cooling the incompletely autenitized material does not require ferrite
nucleation and the c–a transformation starts at relative high temperatures. For B + M, in contrast, nucleation of ferrite is needed and the transformation starts at lower temperatures. As a result the B + M material develops a higher martensite content as well as a higher density of geometrically necessary
dislocations (GNDs). It is speculated that for the B + M material the c–a transformation occurs through a bainitic (i.e. partly displacive) process while the transformation at higher temperatures in the P + F material proceeds exclusively in a diffusive way.

The mechanical performance of multi-phase steel microstructures critically depends on the constituents' chemical and morphological constitutions, which in combination determine the composite hardness, the onset of plasticity, internal load and strain-partitioning, as well as the stability and transformation ki-netics of retained austenite in case of TRIP steels. The novel approach of utilising temporary vessel phases, hence termed vessel microstructure design, enables the tuning of constituent phase properties by linking their formation to a controllable landscape of chemical gradients. This approach hinges on the introduction of alloy carbides as a temporary container, or 'vessel' phase, deliberately producing localised enrichment of alloying elements in a structure predetermined by preliminary heat treatments, referred to as conditioning and accumulation stages. These vessel carbides, which act as reservoirs for specific alloying elements, are then partially dissolved through flash heating, leading to a self-organising landscape of alloying elements in the vicinity of the dissolving particles. The resulting three-or multiple phase microstructures then consist of confined laminates incorporating retained carbides, enveloped by retained austenite shells, embedded within a martensitic matrix. Such complex yet entirely self-organized microstructures offer unique opportunities for strain and load partitioning which we refer to as core-shell micromechanics. Different variants of these core-shell composite structures are produced and examined together with reference microstructures by tensile testing, hardness mappings, impact toughness, X-ray measurements, as well as by electron microscopy. It is found that these novel micro-structures, when tempered, exhibit ultra-high strength and delayed necking, enabled by a combination of gradual strain-hardening and transformation-induced plasticity that is tuneable via control of the initial carbide structure.

The formation of submicron structural defects within austenite (γ), ε-and α′-martensite during cold rolling was followed in a 17.6 wt.% Mn steel. Several probes, including XRD, EBSD, and ECCI-imaging, were used to reveal the complex superposition of the strain hardening mechanisms of these phases. The maximum amount of ε-martensite is observed at a strain of ε = 0.11. At larger strains, the amount of ε decreases suggesting that it precedes the α′-formation (γ → ε → α′). Stacking faults and twins are the main planar defects noticed in ε-martensite. The remaining γ is finely subdivided by stacking faults and twins up to ε = 0.22. From ε = 0.51 on, twinning and multiplication of dislocations are the principal strain hardening mechanisms in austenite. Deformation is accommodated in α′ by the rearrangement of dislocation tangles into dislocation cells plus shear banding at ε = 1.56. During cold rolling, austenite develops a Brass-type texture component, which can be associated to mechanical twinning. ε-martensite presents its basal planes tilted ∼24° from the normal direction towards the rolling direction. The α′-martensite develops and strengthens both, the bcc α-and γ-texture fibers during cold rolling.