论文部分内容阅读
研究了Mg-4Zn-2A1-2Sn合金在225,250和275℃挤压变形后的微观组织、织构及其力学性能.结果表明:在3种挤压温度下合金均发生了完全动态再结晶,晶粒尺寸分别为4.4,7.1和10.5μm.挤压温度直接影响到晶粒内部第二相的析出,在225℃挤压时,在晶粒内部可观察到尺寸为20~60 nm的不规则形貌的Mg_2Sn析出相,挤压温度升高到275℃,第二相析出增多,Mg_2Sn颗粒长大到500 nm左右,并观察到沿挤压方向呈流线分布的微米级Mg_(32)(Al,Zn)_(49).在225和250℃挤压时,形成了单一的平行于挤压方向的基面织构,当温度升高到275℃时,棱柱面滑移临界剪切成力急剧降低,棱柱面滑移系启动,形成了除基而织构以外的棱柱面平行于挤压方向的{1010}<0002>织构,这种取向在沿挤压方向压缩时,压应力平行于c轴方向,不利于拉伸孪晶{1012}<1011>的形成,导致275℃挤压样品拉压不对称性不明显,压缩与拉伸屈服强度之比为0.95.
The microstructures, textures and mechanical properties of Mg-4Zn-2A1-2Sn alloy after extrusion at 225, 250 and 275 ℃ were studied.The results show that all dynamic recrystallization, The grain sizes were 4.4, 7.1 and 10.5 μm, respectively.The extrusion temperature had a direct effect on the precipitation of the second phase inside the grain, and irregularities of 20-60 nm in size were observed inside the grain at 225 ° C Mg2Sn precipitates. When the extrusion temperature is raised to 275 ℃, the second phase precipitates more and the Mg2Sn particles grow up to about 500 nm. Micrometer Mg_ (32) (Al , Zn) (49) .When extruded at 225 and 250 ℃, the formation of a single parallel to the extrusion direction of the base texture, when the temperature rises to 275 ℃, the prismatic plane shear critical shear force Sharp decline, the prism surface slip system is activated, forming a base except for the texture of the prism parallel to the direction of the {1010} <0002> texture, this orientation in the extrusion direction of compression, parallel to the compressive stress In the c-axis direction, it is not conducive to the formation of {1012} <1011> tensile twins, resulting in a slight asymmetry between tensile and compressive strength at 275 ℃. The ratio of compressive strength to tensile yield strength is 0.95.