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
Gas pool coupled activating TIG(GPCA?TIG) welding put forward in?house can dramatically enhance weld penetration of TIG welding through introducing active element oxygen to reverse the Marangoni convection flow in the...Gas pool coupled activating TIG(GPCA?TIG) welding put forward in?house can dramatically enhance weld penetration of TIG welding through introducing active element oxygen to reverse the Marangoni convection flow in the molten pool. In order to further improve the welding productivity, the normal solid tungsten electrode is replaced by a kind of coupling arc electrode. The changes of arc pressure distribution along anode surface and the weld appearance were evaluated. On this basis, the dependences of weld shape characterized with weld depth, width and undercut on the main welding parameters were discussed. The results indicate, the substitution of coupling arc electrode can lead to an obvious decrease of arc pressure. Compared to hollow tungsten electrode and twin tungsten electrodes, the coupling arc electrode is much easier to manufacture and has more compacter structure. Combined with the symmetric distribution of arc pressure in di erent directions, this electrode has extensive adaptability. In the GPCA?TIG welding with coupling arc electrode, both the substitution of coupling arc electrode and the introduction of outer active gas oxygen can reduce the possibilities of producing humping bead and undercut. Their joint action makes this welding method have the capability of realizing high travel speed and deep penetration welding.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National Natural Science Foundation of China(Grant No.51265029)
文摘Gas pool coupled activating TIG(GPCA?TIG) welding put forward in?house can dramatically enhance weld penetration of TIG welding through introducing active element oxygen to reverse the Marangoni convection flow in the molten pool. In order to further improve the welding productivity, the normal solid tungsten electrode is replaced by a kind of coupling arc electrode. The changes of arc pressure distribution along anode surface and the weld appearance were evaluated. On this basis, the dependences of weld shape characterized with weld depth, width and undercut on the main welding parameters were discussed. The results indicate, the substitution of coupling arc electrode can lead to an obvious decrease of arc pressure. Compared to hollow tungsten electrode and twin tungsten electrodes, the coupling arc electrode is much easier to manufacture and has more compacter structure. Combined with the symmetric distribution of arc pressure in di erent directions, this electrode has extensive adaptability. In the GPCA?TIG welding with coupling arc electrode, both the substitution of coupling arc electrode and the introduction of outer active gas oxygen can reduce the possibilities of producing humping bead and undercut. Their joint action makes this welding method have the capability of realizing high travel speed and deep penetration welding.
