In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were...In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were first compressed into the die cavity,then sequentially flowed downward through a 90°corner and two 120°shear steps.The total strain of B-ECAP process could reach 3.924 in a single pass.The results of microstructure observation showed that DRX occurred at upsetting process in the die cavity and completed at position D.The grains were refined to 6.3μm at being extruded at 300℃ and grew obviously with the extrusion temperature increase.The shear tress induced by 900 corner and two 120°shear steps resulted in the basal poles of most grains tilted to extrusion direction(ED)by±25°.Compared with the original billets,the extruded sheets exhibited higher yield strengths(YS),which was mainly attributed to the grain refinement.The higher Schmid factor caused by ED-tilt texture resulted in a fracture elongation(FE)more than that of the original bar in ED,while was equivalent to that in transverse direction(TD).As the extrusion temperature increased,the variation of UTS and YS in ED and TD decreased gradually without ductility obviously decrease.展开更多
To explore the hot compression behavior and microstructural evolution,fine-grained Al−1.88Mg−0.18Sc−0.084Er(wt.%)aluminum alloy wires were fabricated with Castex(continuous casting−extrusion)and ECAP-Conform,and their...To explore the hot compression behavior and microstructural evolution,fine-grained Al−1.88Mg−0.18Sc−0.084Er(wt.%)aluminum alloy wires were fabricated with Castex(continuous casting−extrusion)and ECAP-Conform,and their hot compression behavior was investigated at temperatures of 673−793 K and strain rates of 0.001−10 s−1;the microstructures were characterized by optical microscope,X-ray diffractometer,transmission electron microscope,and electron backscattered diffractometer,and the flow stresses were obtained by thermal compression simulator.Microstructural evolution and flow curves reveal that dynamic recovery is the dominant softening mechanism.Continuous dynamic recrystallization followed by dynamic grain growth takes place at a temperature of 773 K and a strain rate of 0.001 s−1;the yielding drop phenomenon was discovered.Hyperbolic sine constitutive equation incorporating dislocation variables was presented,and a power law constitutive equation was established.The stress exponent is 3.262,and the activation energy for deformation is 154.465 kJ/mol,indicating that dislocation viscous glide is the dominant deformation mechanism.展开更多
基金Projects(52274397,52275382)supported by the National Natural Science Foundation of ChinaProject(tsqn202211115)supported by the Taishan Scholars Program of Shandong Province,China+2 种基金Project supported by the Yantai High-end Talent Introduction“Double Hundred Plan”(2021),ChinaProject(ZR2024JQ020)supported by the Shandong Provincial Natural Science Foundation of ChinaProjects(CZ20210034,CM20223013)supported by the Changzhou Sci&Tech Program,China。
文摘In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were first compressed into the die cavity,then sequentially flowed downward through a 90°corner and two 120°shear steps.The total strain of B-ECAP process could reach 3.924 in a single pass.The results of microstructure observation showed that DRX occurred at upsetting process in the die cavity and completed at position D.The grains were refined to 6.3μm at being extruded at 300℃ and grew obviously with the extrusion temperature increase.The shear tress induced by 900 corner and two 120°shear steps resulted in the basal poles of most grains tilted to extrusion direction(ED)by±25°.Compared with the original billets,the extruded sheets exhibited higher yield strengths(YS),which was mainly attributed to the grain refinement.The higher Schmid factor caused by ED-tilt texture resulted in a fracture elongation(FE)more than that of the original bar in ED,while was equivalent to that in transverse direction(TD).As the extrusion temperature increased,the variation of UTS and YS in ED and TD decreased gradually without ductility obviously decrease.
基金The authors are grateful for the financial support from the Key Project of the National Natural Science Foundation of China(51334006).
文摘To explore the hot compression behavior and microstructural evolution,fine-grained Al−1.88Mg−0.18Sc−0.084Er(wt.%)aluminum alloy wires were fabricated with Castex(continuous casting−extrusion)and ECAP-Conform,and their hot compression behavior was investigated at temperatures of 673−793 K and strain rates of 0.001−10 s−1;the microstructures were characterized by optical microscope,X-ray diffractometer,transmission electron microscope,and electron backscattered diffractometer,and the flow stresses were obtained by thermal compression simulator.Microstructural evolution and flow curves reveal that dynamic recovery is the dominant softening mechanism.Continuous dynamic recrystallization followed by dynamic grain growth takes place at a temperature of 773 K and a strain rate of 0.001 s−1;the yielding drop phenomenon was discovered.Hyperbolic sine constitutive equation incorporating dislocation variables was presented,and a power law constitutive equation was established.The stress exponent is 3.262,and the activation energy for deformation is 154.465 kJ/mol,indicating that dislocation viscous glide is the dominant deformation mechanism.
