The ductility and plastic asymmetry of an as-annealed magnesium alloy plate were studied in compression through combined process of torsion and subsequent annealing by optical microscope and EBSD. The yield strength（YS） and ultimate compression strength（UCS） as well as the compression ductility（CD） were simultaneously raised by prior torsion at room temperature. The CD was further enhanced by subsequent annealing. Also, the torqued sample followed by annealing experienced a rising CD with the increase in prior strain, leading to the maximum true strain of 0.279, which is twice that of the as-annealed original one. The sample showed a largely reduced tension-compression yield asymmetry by subjecting to pre-torsion alone or combined with a subsequent annealing. The enhanced ductility and reduced asymmetry are attributed to the development of a gradient microstructure with refined grains, and also randomization of the weakened texture due to torsion and subsequent annealing.
In the present study,mechanical property,microstructure and texture of an extruded Mg–1.0Al–1.5Ca–1.0Mn(wt.%)flat-oval tube in both the flat and the oval regions were systematically studied.Our results show that there exists a great difference in microstructure and texture between the flat and the oval regions.Both the flat and the oval regions have fine DRXed grains of 3–4μm,while more row stacked grains are observed in the flat region.A large number of fine particles with a size of about 0.5μm are dispersed in both the grain boundary and grain interior.The particles exhibit a uniform distribution in the oval region,while they tend to aggregate into bands along the extrusion direction(ED)in the flat region.The texture in the oval region is similar to that in extruded Mg rods with a preferred distribution of prismatic planes and random distribution of(0002)poles around the ED,while that in the flat region is close to that in extruded sheets containing two texture components,<0002>//normal direction(ND)and<0002>//transverse direction(TD).A high fraction of<0002>//TD component,about 52–62%,is observed in the flat region.The flat region has a tensile yield strength of 254 MPa,an ultimate tensile strength of 290 MPa and an elongation to failure of 4.3%.
Feilong GuoBo FengShiwei FuYunchang XinShiwei XuQing Liu
In the present study,the texture evolution and mechanical anisotropy in a typical Mg–Zn–Ca alloy through hot cross rolling(CR)and unidirectional rolling(UR)were systematically studied.The results show that the rolling path greatly affects the annealed texture.The UR develops a texture with basal poles mainly distributing along the transverse direction(TD).By contrast,an ellipse-like(0002)texture with basal pole inclining largely away from the normal direction(ND)is developed after hot cross rolling and annealing.Therefore,the CR is an effective method to tailor the texture of the experimental alloy.Unfortunately,this ellipse-like texture could not reserve during the subsequent unidirectional hot rolling and annealing.Both UR and CR plates exhibit a strong planar mechanical anisotropy compared with the traditional unidirectional rolled plate.
Experiments and visco-plastic self-consistent (VPSC) simulations were used to quantify the amount of twinning and the relationship to stress?strain behavior in a textured Mg?3Al?1Zn plate. Two different compression directions were utilized to favor{1012} extension or{1011} compression twinning.{1012} twins nucleate at the beginning of plastic deformation and grow to consume the parent grains completely. During compression along the normal direction,{1011} twinning and{1011}?{1012} double twinning start at strain of 0.05, and the number of twins increases until rupture, above strain of 0.15.{1011} and{1011}?{1012} twinning also occur during compression along the transverse direction, start at strain of 0.06 and then multiply in grains totally reoriented by{1012} twins. Using suitable parameters, the VPSC model can accurately predict the occurrence of extension, compression and double-twinning as well as the flow stresses and deformed textures. According to VPSC simulations, twinning and slip have the same latent hardening parameters.
In the present study,the influence of solute atoms together with dislocations at {101^-2} twin boundary（TB） on mechanical behavior of a detwinning predominant deformation in a Mg alloy AZ31 plate was systematically studied.The results show that a large number of {101^-2} twins disappear during recompression along the normal direction.Both the TB-dislocation interaction and TB-solute-dislocation interaction can greatly enhance the yield stress of the recompression along the normal direction（ND）.However,the solute segregation at {1012} TBs with an intensive interaction with 〈a〉 dislocations cannot further enhance the yield stress of ND recompression.The samples with TB-dislocation interaction show a similar working hardening performance with that subjected to a TB-solute-dislocation interaction.Both the TB-dislocation interaction and TB-solute-dislocation interaction greatly reduce the value of work hardening peaks during a detwinning predominant deformation.
Jing XuBo GuanHuihui YuXuezhen CaoYunchang XinQing Liu
