The influence of the texture, strain rate and temper on the behaviour of an extruded AA7030 alumi... more The influence of the texture, strain rate and temper on the behaviour of an extruded AA7030 aluminium alloy is studied by uniaxial tensile tests. The results show that the texture has a strong impact on plastic flow and ductility. However, its influence on yield strength, ultimate strength and strain-hardening capacity is less. The temper conditions strongly affect the yield and ultimate strengths and strain-hardening capability, while their influence on plastic flow is limited. It was also found that the strain rate does not have an important influence on the plastic flow and the yield strength in temper W. While the ultimate strength and strain-hardening decrease significantly with increasing strain rate, the ductility increases. A metallographic study found that failure occurs by shear band formation subsequent to diffuse and local necking. Microscopic voids are formed in coarse slip bands prior to crack initiation. Fracture surface observations show that there is a high density of two different dimple sizes.
The potential for significant grain refinement in pure aluminium (99.9%) processed by means of eq... more The potential for significant grain refinement in pure aluminium (99.9%) processed by means of equal channel angular pressing at 523 K (T/T m ∼ 0.6) has been demonstrated. The mean grain size was significantly reduced from 1.2 mm to 4 µm after eight passes. The stored energy and high-angle grain boundary fraction increase until 6 passes and then remain almost constant until 8 passes. The grain refinement occurred in two stages, initially driven by the evolution of deformation inhomogeneties (deformation bands, microbands) and then through recovery and the interaction of deformation inhomogeneties into fine grains.
... Phys. Lett. 83, 632 (2003). MPLiu, HJRoven, and YDYu, Int. J. Mat. Res. (to be published). MP... more ... Phys. Lett. 83, 632 (2003). MPLiu, HJRoven, and YDYu, Int. J. Mat. Res. (to be published). MPLiu, HJRoven, YDYu, and JCWerenskiold, Mater. Sci. Eng., AMSAPE30921-5093 (to be published). L.Remy, Scr. Metall. 11, 169 (1977). LCQin, DXLi, and KHKuo, Philos. Mag. ...
The plastic anisotropy of two recrystallized and two unrecrystallized extruded profiles is analys... more The plastic anisotropy of two recrystallized and two unrecrystallized extruded profiles is analysed. Tensile tests in the solutionised condition show strong directionality of properties. The texture is very strong and changes slightly during deformation. The stress-strain curves are corrected by the Taylor factor, calculated from the texture measurements. This gives critical resolved shear stress as a function of resolved shear strain. Assuming that the texture is responsible for all the anisotropy, the shear stress-strain curves in the various directions should coincide. This is partly true for the unrecrystallized alloys but not for recrystallized alloys. This is thought to be related to variations in slip activity in cube grains.
The boundary structure of } 1 1 10 { deformation twins formed in commercial pure titanium (CP-T... more The boundary structure of } 1 1 10 { deformation twins formed in commercial pure titanium (CP-Ti) during the initial pass ECAP processing has been studied by TEM and HRTEM. A new twining mode with twinning dislocation of b3/3, has been identified by a dichromatic diagram method. The new mode of } 1 1 10 { twin has substantially higher interface energy and accommodates more shear strain during deformation than the conventional b4 twinning mode. The deviation angle between the habit trace of the twin boundary and the theoretical twinning plane, K1, is dependent upon the density of twin dislocations. Over the last decades, severe plastic deformation (SPD) has been demonstrated as an effective method to produce bulk ultra-fine grained (UFG) and nano structured metals, for example Al, Mg, Fe, Ni and Ti, as reviewed in [1,2]. Much work has been done on the deformation behaviour of face centred cubic (FCC) metals during SPD [3-5]. However, studies on the deformation behaviour, especial...
Transient liquid phase (TLP) bonding of Al-6063 and UNS S32304 was performed using copper foil as... more Transient liquid phase (TLP) bonding of Al-6063 and UNS S32304 was performed using copper foil as an interlayer between the base metals. A compression load was applied normal to the specimens. Metallurgical examination of the produced joints showed three distinct regions including a reaction zone, diffusion affected zone and the base metals. The diffusion of copper into aluminum resulted in an Al-Cu eutectic structure. However, the oxide layer on the aluminum surface controlled the dissolution behavior of copper and the extent of its wettability with the base metals. Although voids and intermetallic compounds were detected at the interfaces of the processed joints, a defect free joint was produced at…
The International Journal of Advanced Manufacturing Technology
Aluminium alloys processed by wire arc additive manufacturing (WAAM) exhibit a relatively coarse ... more Aluminium alloys processed by wire arc additive manufacturing (WAAM) exhibit a relatively coarse microstructure with a columnar morphology. A powerful measure to refine the microstructure and to enhance mechanical properties is to promote grain refinement during solidification. Addition of ceramic nanoparticles has shown great potential as grain refiner and strengthening phase in aluminium alloys. Thus, an Al-Mg alloy mixed with TiC nanoparticles was manufactured by the novel metal screw extrusion method to a wire and subsequently deposited by WAAM. Measures to restrict oxidation of magnesium during metal screw extrusion were examined. Purging of CO2 gas into the extrusion chamber resulted in a remarkable reduction in formation of MgO and Mg(OH)2. TiC decomposed to Al3Ti during WAAM deposition, leading to a significant grain refinement of 93% compared to a commercial benchmark. The presence of remaining TiC nanoparticles accounted for an increased hardness of the WAAM material throu...
The microstructure evolution of an AZ31 Mg alloy during cyclic extrusion compression (CEC) is inv... more The microstructure evolution of an AZ31 Mg alloy during cyclic extrusion compression (CEC) is investigated by optical microscopy, TEM and electron backscatter diffraction (EBSD). The mean grain size of 1.77 μm with fine grains of 150 ± 50 nm for AZ31 alloy is obtained after CEC ...
Processing of aluminum alloys by wire arc additive manufacturing (WAAM) gained significant attent... more Processing of aluminum alloys by wire arc additive manufacturing (WAAM) gained significant attention from industry and academia in the last decade. With the possibility to create large and relatively complex parts at low investment and operational expenses, WAAM is well-suited for implementation in a range of industries. The process nature involves fusion melting of a feedstock wire by an electric arc where metal droplets are strategically deposited in a layer-by-layer fashion to create the final shape. The inherent fusion and solidification characteristics in WAAM are governing several aspects of the final material, herein process-related defects such as porosity and cracking, microstructure, properties, and performance. Coupled to all mentioned aspects is the alloy composition, which at present is highly restricted for WAAM of aluminum but received considerable attention in later years. This review article describes common quality issues related to WAAM of aluminum, i.e., porosity...
The influence of the texture, strain rate and temper on the behaviour of an extruded AA7030 alumi... more The influence of the texture, strain rate and temper on the behaviour of an extruded AA7030 aluminium alloy is studied by uniaxial tensile tests. The results show that the texture has a strong impact on plastic flow and ductility. However, its influence on yield strength, ultimate strength and strain-hardening capacity is less. The temper conditions strongly affect the yield and ultimate strengths and strain-hardening capability, while their influence on plastic flow is limited. It was also found that the strain rate does not have an important influence on the plastic flow and the yield strength in temper W. While the ultimate strength and strain-hardening decrease significantly with increasing strain rate, the ductility increases. A metallographic study found that failure occurs by shear band formation subsequent to diffuse and local necking. Microscopic voids are formed in coarse slip bands prior to crack initiation. Fracture surface observations show that there is a high density of two different dimple sizes.
The potential for significant grain refinement in pure aluminium (99.9%) processed by means of eq... more The potential for significant grain refinement in pure aluminium (99.9%) processed by means of equal channel angular pressing at 523 K (T/T m ∼ 0.6) has been demonstrated. The mean grain size was significantly reduced from 1.2 mm to 4 µm after eight passes. The stored energy and high-angle grain boundary fraction increase until 6 passes and then remain almost constant until 8 passes. The grain refinement occurred in two stages, initially driven by the evolution of deformation inhomogeneties (deformation bands, microbands) and then through recovery and the interaction of deformation inhomogeneties into fine grains.
... Phys. Lett. 83, 632 (2003). MPLiu, HJRoven, and YDYu, Int. J. Mat. Res. (to be published). MP... more ... Phys. Lett. 83, 632 (2003). MPLiu, HJRoven, and YDYu, Int. J. Mat. Res. (to be published). MPLiu, HJRoven, YDYu, and JCWerenskiold, Mater. Sci. Eng., AMSAPE30921-5093 (to be published). L.Remy, Scr. Metall. 11, 169 (1977). LCQin, DXLi, and KHKuo, Philos. Mag. ...
The plastic anisotropy of two recrystallized and two unrecrystallized extruded profiles is analys... more The plastic anisotropy of two recrystallized and two unrecrystallized extruded profiles is analysed. Tensile tests in the solutionised condition show strong directionality of properties. The texture is very strong and changes slightly during deformation. The stress-strain curves are corrected by the Taylor factor, calculated from the texture measurements. This gives critical resolved shear stress as a function of resolved shear strain. Assuming that the texture is responsible for all the anisotropy, the shear stress-strain curves in the various directions should coincide. This is partly true for the unrecrystallized alloys but not for recrystallized alloys. This is thought to be related to variations in slip activity in cube grains.
The boundary structure of } 1 1 10 { deformation twins formed in commercial pure titanium (CP-T... more The boundary structure of } 1 1 10 { deformation twins formed in commercial pure titanium (CP-Ti) during the initial pass ECAP processing has been studied by TEM and HRTEM. A new twining mode with twinning dislocation of b3/3, has been identified by a dichromatic diagram method. The new mode of } 1 1 10 { twin has substantially higher interface energy and accommodates more shear strain during deformation than the conventional b4 twinning mode. The deviation angle between the habit trace of the twin boundary and the theoretical twinning plane, K1, is dependent upon the density of twin dislocations. Over the last decades, severe plastic deformation (SPD) has been demonstrated as an effective method to produce bulk ultra-fine grained (UFG) and nano structured metals, for example Al, Mg, Fe, Ni and Ti, as reviewed in [1,2]. Much work has been done on the deformation behaviour of face centred cubic (FCC) metals during SPD [3-5]. However, studies on the deformation behaviour, especial...
Transient liquid phase (TLP) bonding of Al-6063 and UNS S32304 was performed using copper foil as... more Transient liquid phase (TLP) bonding of Al-6063 and UNS S32304 was performed using copper foil as an interlayer between the base metals. A compression load was applied normal to the specimens. Metallurgical examination of the produced joints showed three distinct regions including a reaction zone, diffusion affected zone and the base metals. The diffusion of copper into aluminum resulted in an Al-Cu eutectic structure. However, the oxide layer on the aluminum surface controlled the dissolution behavior of copper and the extent of its wettability with the base metals. Although voids and intermetallic compounds were detected at the interfaces of the processed joints, a defect free joint was produced at…
The International Journal of Advanced Manufacturing Technology
Aluminium alloys processed by wire arc additive manufacturing (WAAM) exhibit a relatively coarse ... more Aluminium alloys processed by wire arc additive manufacturing (WAAM) exhibit a relatively coarse microstructure with a columnar morphology. A powerful measure to refine the microstructure and to enhance mechanical properties is to promote grain refinement during solidification. Addition of ceramic nanoparticles has shown great potential as grain refiner and strengthening phase in aluminium alloys. Thus, an Al-Mg alloy mixed with TiC nanoparticles was manufactured by the novel metal screw extrusion method to a wire and subsequently deposited by WAAM. Measures to restrict oxidation of magnesium during metal screw extrusion were examined. Purging of CO2 gas into the extrusion chamber resulted in a remarkable reduction in formation of MgO and Mg(OH)2. TiC decomposed to Al3Ti during WAAM deposition, leading to a significant grain refinement of 93% compared to a commercial benchmark. The presence of remaining TiC nanoparticles accounted for an increased hardness of the WAAM material throu...
The microstructure evolution of an AZ31 Mg alloy during cyclic extrusion compression (CEC) is inv... more The microstructure evolution of an AZ31 Mg alloy during cyclic extrusion compression (CEC) is investigated by optical microscopy, TEM and electron backscatter diffraction (EBSD). The mean grain size of 1.77 μm with fine grains of 150 ± 50 nm for AZ31 alloy is obtained after CEC ...
Processing of aluminum alloys by wire arc additive manufacturing (WAAM) gained significant attent... more Processing of aluminum alloys by wire arc additive manufacturing (WAAM) gained significant attention from industry and academia in the last decade. With the possibility to create large and relatively complex parts at low investment and operational expenses, WAAM is well-suited for implementation in a range of industries. The process nature involves fusion melting of a feedstock wire by an electric arc where metal droplets are strategically deposited in a layer-by-layer fashion to create the final shape. The inherent fusion and solidification characteristics in WAAM are governing several aspects of the final material, herein process-related defects such as porosity and cracking, microstructure, properties, and performance. Coupled to all mentioned aspects is the alloy composition, which at present is highly restricted for WAAM of aluminum but received considerable attention in later years. This review article describes common quality issues related to WAAM of aluminum, i.e., porosity...
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Papers by Hans Roven