Introduction Shape of precipitates in alloys is affected by various factors. Although both Cu and... more Introduction Shape of precipitates in alloys is affected by various factors. Although both Cu and Ag have a FCC structure, the difference in lattice constants between them is about 12%. When Ag particles precipitate in a Cu matrix, the difference in lattice constants is accommodated elastically and/or plastically. The accommodation affects the shape and elastic state of the Ag precipitates. It is well known that discontinuous precipitation starting from grain boundaries occurs in polycrystalline Cu-Ag alloys. As far as we know, there is very few reports on precipitation of isolated Ag particles in grains of Cu-Ag alloys. In the present study, we observe the shapes of the isolated Ag precipitates with the size of few to ten nm in single crystals of a Cu-Ag alloy. The shape change of the Ag precipitates during the growth of the precipitates is discussed.
A cell structure development and a crack initiation during a fatigue of an Fe-3 mass%Si alloy was... more A cell structure development and a crack initiation during a fatigue of an Fe-3 mass%Si alloy was investigated through electron channeling contrast imaging in a scanning electron microscope and electron back-scatter diffraction analysis. The crystal rotation regions (CRRs), deformation bands (DBs), and cell bands (CBs) together formed a hierarchy in the dislocation structures. In the early stage of fatigue, deformation is constrained near grain boundaries; this impedes further dislocation propagation. This restriction is attributed the formation of CRRs with a width of several hundred micrometers. Further, DBs that were several microns wide were developed inside the CRRs, and CBs with a width of several hundred nanometers were formed inside the DBs. Meanwhile, a crack was initiated from a CRR near a grain boundary. At the crack tip, a DB penetrating the CRR was formed parallel to the crack-propagation direction. It was elucidated that the cell boundary in the DB had a high misorientation angle of approximately 10 degrees, which greatly affected to the crack initiation. In addition, the penetrating DB was composed of elongated cells and cell bands. Prior to crack initiation, the boundaries of the cell bands evolved in proportion to the increasing dislocation density during fatigue. The elongated direction of the cell boundary, which was almost parallel to the {110} plane with a tilt boundary feature, dominated the crack-propagation direction. The formation plane and the cell boundary development process can be explained by analyzing the geometrical relationship of the activated slip systems between adjacent cells.
Proceedings of the 8th Pacific Rim International Congress on Advanced Materials and Processing, 2013
The distributions of the local internal stress near the grain boundaries in 20 % cold-rolled SUS3... more The distributions of the local internal stress near the grain boundaries in 20 % cold-rolled SUS316 stainless steel were measured under the external tensile stress of 0 and 300 MPa using the Energy-dispersive X-ray Diffraction Microscopy (EXDM) technique at BL28B2 of SPring-8. The local internal stresses near the grain boundaries were successfully evaluated. The results indicated that the evidence that the internal stress concentration was occurred at the grain boundaries under the external tensile stress.
The development of solventless system for modulating properties of network materials is imperativ... more The development of solventless system for modulating properties of network materials is imperative for the next generation sustainable technology. Utilization of photostimulation is important owing to its spatial and temporal locality, yet designing photoresponsive network materials exhibiting repeatable and dramatic change in their properties remains a challenge. Here, the authors report a photocleavable regenerative network (PRN) linked with photoresponsive hexaarylbiimidazoles (HABIs) synthesized from narrow dispersity star‐shaped poly(dimethylsiloxane)s (PDMSs) having 2,4,5‐triphenylimidazole end groups. The use of urea anion as a catalyst for ring opening polymerization (ROP) of cyclic siloxane initiated from silanols enables control of molecular weight and dispersity. The rheological measurements for the synthesized PRNs exhibit drastic changes in storage and loss moduli (G′ and G″) upon photoirradiation in the solid state (G′ > G″). This photocontrolled change in viscoelasticity with retaining solidity enables application of PRNs as a remotely‐controlled photo‐melt adhesive and photo‐scissible string. The developed PRNs will enable a wide variety of applications such as industrially important next‐generation sustainable adhesive, sealant, and reversibly‐deformable 3D printing materials with their spatially and temporally local manipulability, solventless handleability, and excellent reversibility.
Abstract This work investigates deformation bands (DBs) in copper single crystals with the stress... more Abstract This work investigates deformation bands (DBs) in copper single crystals with the stress axis oriented in the direction of the coplanar-double-slip. The characteristics of DBs with kink bands are studied via multiple-plane observation by scanning electron microscopy, and electron back-scattered diffraction. An inhomogeneous deformation causes DBs to form in double-slip-oriented copper single crystals at comparatively low plastic strain (less than 1%). When the coplanar-double slip system is active, the DB plane is perpendicular to both the coplanar-slip plane and the sum of the Burgers vectors for the activated slip systems (i.e., the {211} plane). The DB regions are rotated approximately 10 degrees with respect to the matrix. Furthermore, a cell-like dislocation structure develops in the DB. The relationship between the deformation behavior and the activated slip systems is well explained by studying the crystallographic features of the DB, which improves our understanding of inhomogeneous deformation in single crystals.
Introduction Shape of precipitates in alloys is affected by various factors. Although both Cu and... more Introduction Shape of precipitates in alloys is affected by various factors. Although both Cu and Ag have a FCC structure, the difference in lattice constants between them is about 12%. When Ag particles precipitate in a Cu matrix, the difference in lattice constants is accommodated elastically and/or plastically. The accommodation affects the shape and elastic state of the Ag precipitates. It is well known that discontinuous precipitation starting from grain boundaries occurs in polycrystalline Cu-Ag alloys. As far as we know, there is very few reports on precipitation of isolated Ag particles in grains of Cu-Ag alloys. In the present study, we observe the shapes of the isolated Ag precipitates with the size of few to ten nm in single crystals of a Cu-Ag alloy. The shape change of the Ag precipitates during the growth of the precipitates is discussed.
A cell structure development and a crack initiation during a fatigue of an Fe-3 mass%Si alloy was... more A cell structure development and a crack initiation during a fatigue of an Fe-3 mass%Si alloy was investigated through electron channeling contrast imaging in a scanning electron microscope and electron back-scatter diffraction analysis. The crystal rotation regions (CRRs), deformation bands (DBs), and cell bands (CBs) together formed a hierarchy in the dislocation structures. In the early stage of fatigue, deformation is constrained near grain boundaries; this impedes further dislocation propagation. This restriction is attributed the formation of CRRs with a width of several hundred micrometers. Further, DBs that were several microns wide were developed inside the CRRs, and CBs with a width of several hundred nanometers were formed inside the DBs. Meanwhile, a crack was initiated from a CRR near a grain boundary. At the crack tip, a DB penetrating the CRR was formed parallel to the crack-propagation direction. It was elucidated that the cell boundary in the DB had a high misorientation angle of approximately 10 degrees, which greatly affected to the crack initiation. In addition, the penetrating DB was composed of elongated cells and cell bands. Prior to crack initiation, the boundaries of the cell bands evolved in proportion to the increasing dislocation density during fatigue. The elongated direction of the cell boundary, which was almost parallel to the {110} plane with a tilt boundary feature, dominated the crack-propagation direction. The formation plane and the cell boundary development process can be explained by analyzing the geometrical relationship of the activated slip systems between adjacent cells.
Proceedings of the 8th Pacific Rim International Congress on Advanced Materials and Processing, 2013
The distributions of the local internal stress near the grain boundaries in 20 % cold-rolled SUS3... more The distributions of the local internal stress near the grain boundaries in 20 % cold-rolled SUS316 stainless steel were measured under the external tensile stress of 0 and 300 MPa using the Energy-dispersive X-ray Diffraction Microscopy (EXDM) technique at BL28B2 of SPring-8. The local internal stresses near the grain boundaries were successfully evaluated. The results indicated that the evidence that the internal stress concentration was occurred at the grain boundaries under the external tensile stress.
The development of solventless system for modulating properties of network materials is imperativ... more The development of solventless system for modulating properties of network materials is imperative for the next generation sustainable technology. Utilization of photostimulation is important owing to its spatial and temporal locality, yet designing photoresponsive network materials exhibiting repeatable and dramatic change in their properties remains a challenge. Here, the authors report a photocleavable regenerative network (PRN) linked with photoresponsive hexaarylbiimidazoles (HABIs) synthesized from narrow dispersity star‐shaped poly(dimethylsiloxane)s (PDMSs) having 2,4,5‐triphenylimidazole end groups. The use of urea anion as a catalyst for ring opening polymerization (ROP) of cyclic siloxane initiated from silanols enables control of molecular weight and dispersity. The rheological measurements for the synthesized PRNs exhibit drastic changes in storage and loss moduli (G′ and G″) upon photoirradiation in the solid state (G′ > G″). This photocontrolled change in viscoelasticity with retaining solidity enables application of PRNs as a remotely‐controlled photo‐melt adhesive and photo‐scissible string. The developed PRNs will enable a wide variety of applications such as industrially important next‐generation sustainable adhesive, sealant, and reversibly‐deformable 3D printing materials with their spatially and temporally local manipulability, solventless handleability, and excellent reversibility.
Abstract This work investigates deformation bands (DBs) in copper single crystals with the stress... more Abstract This work investigates deformation bands (DBs) in copper single crystals with the stress axis oriented in the direction of the coplanar-double-slip. The characteristics of DBs with kink bands are studied via multiple-plane observation by scanning electron microscopy, and electron back-scattered diffraction. An inhomogeneous deformation causes DBs to form in double-slip-oriented copper single crystals at comparatively low plastic strain (less than 1%). When the coplanar-double slip system is active, the DB plane is perpendicular to both the coplanar-slip plane and the sum of the Burgers vectors for the activated slip systems (i.e., the {211} plane). The DB regions are rotated approximately 10 degrees with respect to the matrix. Furthermore, a cell-like dislocation structure develops in the DB. The relationship between the deformation behavior and the activated slip systems is well explained by studying the crystallographic features of the DB, which improves our understanding of inhomogeneous deformation in single crystals.
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Papers by 知孝 宮澤