The work aims to investigate the formation and transformation mechanism of non-basal texture in the extruded Mg alloys.With this purpose a pure Mg as reference and eight Mg-Gd binary alloys with the Gd concentration r...The work aims to investigate the formation and transformation mechanism of non-basal texture in the extruded Mg alloys.With this purpose a pure Mg as reference and eight Mg-Gd binary alloys with the Gd concentration ranging from 0.5 wt.%to 18 wt.%were prepared for extrusion.This study shows that the basal fiber texture in pure Mg transited into RE(rare earth)texture in diluted Mg-Gd alloys and into the abnormal C-texture in high-concentration Mg-Gd alloys.In pure Mg,discontinuous dynamic recrystallization plays a predominant role during the extrusion process,resulting in the formation of a typical basal fiber texture.Alloying with high concentration of Gd impedes the dynamic recrystallization process,facilitating the heterogeneous nucleation of shear bands as well as the dynamic recrystallization within shear bands.Dynamic recrystallized grains within shear bands nucleate with a similar orientation to the host deformed parent grains and gradually tilt their c-axis to the extrusion direction during growth by absorbing dislocations,leading to the formation of either the REtexture orientation or the C-texture orientation,depending on the stored energy within shear bands.The analysis aided by IGMA and TEM characterization reveals that the shear bands originate from the extensive but heterogeneous activation of pyramidal I slip.Tensile tests illustrate a close correlation between the fracture elongation and texture types.A comprehensive understanding of the formation and transformation mechanism of different texture components in Mg alloys holds significant importance for the design of high-performance Mg alloys by texture engineering.展开更多
Dislocation engineering concept has been successfully employed to tackle the strength-ductility trade-off in steels, resulting in the development of high-strength high-ductility deformed and partitioned(D&P)steel....Dislocation engineering concept has been successfully employed to tackle the strength-ductility trade-off in steels, resulting in the development of high-strength high-ductility deformed and partitioned(D&P)steel. The present perspective proposes to employ such dislocation engineering concept to develop strong and ductile magnesium(Mg) alloys. High density of < c + a > dislocations could be generated at appropriate temperature and retained in the Mg alloy after quenching to room temperature. Those < c + a > dislocations inherited from the warm deformation could provide < c + a > dislocation sources when the Mg alloy is deformed at room temperature, resulting in good ductility. The high dislocation density generated at warm deformation provides dislocation forest hardening, leading to improved yield strength of Mg alloy.展开更多
Ultra-high strength alloys with good ductility are ideal materials for lightweight structural application in various industries. However, improving the strength of alloys frequently results in a reduction in ductility...Ultra-high strength alloys with good ductility are ideal materials for lightweight structural application in various industries. However, improving the strength of alloys frequently results in a reduction in ductility, which is known as the strength-ductility trade-off in metallic materials. Current alloy design strategies for improving the ductility of ultra-high strength alloys mainly focus on the selection of alloy composition （atomic length scale） or manipulating ultra-fine and nano-grained microstructure （grain length scale）. The intermediate length scale between atomic and grain scales is the dislocation length scale. A new alloy design concept based on such dislocation length scale, namely dislocation engineering, is illustrated in the present work. This dislocation engineering concept has been successfully substantiated by the design and fabrication of a deformed and partitioned （D＆P） steel with a yield strength of 2,2 GPa and an uniform elongation of 16%. In this D＆P steel, high dislocation density can not only increase strength but also improve ductility. High dislocation density is mainly responsible for the improved yield strength through dislocation forest hardening, whilst the improved ductility is achieved by the glide of intensive mobile dislocations and well-controlled transformation-induced plasticity （TRIP） effect, both of which are governed by the high dislocation density resulting from warm rolling and martensitic transformation during cold rolling. In addition, the present work proposes for the first time to apply such dislocation engineering concept to the quenching and partitioning （Q＆P） steel by incorporating a warm rolling process prior to the quenching step, with an aim to improve simultaneously the strength and ductility of the Q＆P steel. It is believed that dislocation engineering provides a new promising alloy design strategy for producing novel strong and ductile alloys.展开更多
基金funding from the National Natural Science Foundation of China under Grant No 52275327。
文摘The work aims to investigate the formation and transformation mechanism of non-basal texture in the extruded Mg alloys.With this purpose a pure Mg as reference and eight Mg-Gd binary alloys with the Gd concentration ranging from 0.5 wt.%to 18 wt.%were prepared for extrusion.This study shows that the basal fiber texture in pure Mg transited into RE(rare earth)texture in diluted Mg-Gd alloys and into the abnormal C-texture in high-concentration Mg-Gd alloys.In pure Mg,discontinuous dynamic recrystallization plays a predominant role during the extrusion process,resulting in the formation of a typical basal fiber texture.Alloying with high concentration of Gd impedes the dynamic recrystallization process,facilitating the heterogeneous nucleation of shear bands as well as the dynamic recrystallization within shear bands.Dynamic recrystallized grains within shear bands nucleate with a similar orientation to the host deformed parent grains and gradually tilt their c-axis to the extrusion direction during growth by absorbing dislocations,leading to the formation of either the REtexture orientation or the C-texture orientation,depending on the stored energy within shear bands.The analysis aided by IGMA and TEM characterization reveals that the shear bands originate from the extensive but heterogeneous activation of pyramidal I slip.Tensile tests illustrate a close correlation between the fracture elongation and texture types.A comprehensive understanding of the formation and transformation mechanism of different texture components in Mg alloys holds significant importance for the design of high-performance Mg alloys by texture engineering.
文摘Dislocation engineering concept has been successfully employed to tackle the strength-ductility trade-off in steels, resulting in the development of high-strength high-ductility deformed and partitioned(D&P)steel. The present perspective proposes to employ such dislocation engineering concept to develop strong and ductile magnesium(Mg) alloys. High density of < c + a > dislocations could be generated at appropriate temperature and retained in the Mg alloy after quenching to room temperature. Those < c + a > dislocations inherited from the warm deformation could provide < c + a > dislocation sources when the Mg alloy is deformed at room temperature, resulting in good ductility. The high dislocation density generated at warm deformation provides dislocation forest hardening, leading to improved yield strength of Mg alloy.
基金the support from Research Grants Council of Hong Kong (Grants No. 17203014, HKU712713E and 17255016)the National Natural Science Foundation of China (Grant No. U1560204)
文摘Ultra-high strength alloys with good ductility are ideal materials for lightweight structural application in various industries. However, improving the strength of alloys frequently results in a reduction in ductility, which is known as the strength-ductility trade-off in metallic materials. Current alloy design strategies for improving the ductility of ultra-high strength alloys mainly focus on the selection of alloy composition （atomic length scale） or manipulating ultra-fine and nano-grained microstructure （grain length scale）. The intermediate length scale between atomic and grain scales is the dislocation length scale. A new alloy design concept based on such dislocation length scale, namely dislocation engineering, is illustrated in the present work. This dislocation engineering concept has been successfully substantiated by the design and fabrication of a deformed and partitioned （D＆P） steel with a yield strength of 2,2 GPa and an uniform elongation of 16%. In this D＆P steel, high dislocation density can not only increase strength but also improve ductility. High dislocation density is mainly responsible for the improved yield strength through dislocation forest hardening, whilst the improved ductility is achieved by the glide of intensive mobile dislocations and well-controlled transformation-induced plasticity （TRIP） effect, both of which are governed by the high dislocation density resulting from warm rolling and martensitic transformation during cold rolling. In addition, the present work proposes for the first time to apply such dislocation engineering concept to the quenching and partitioning （Q＆P） steel by incorporating a warm rolling process prior to the quenching step, with an aim to improve simultaneously the strength and ductility of the Q＆P steel. It is believed that dislocation engineering provides a new promising alloy design strategy for producing novel strong and ductile alloys.
