研究了Mg-4Zn-2Al-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10.5 μm. 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Mg₂Sn析出相, 挤压温度升高到275 ℃, 第二相析出增多, Mg₂Sn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Mg₃₂(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应力急剧降低, 棱柱面滑移系启动, 形成了除基面织构以外的棱柱面平行于挤压方向的 \{10 {\displaystyle \stackrel{-}{1}} 0\} < 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 \{10 {\displaystyle \stackrel{-}{1}} 2\} 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.

Due to the high demand of light-weight alloys in automotive applications, wrought magnesium (Mg) alloys, applied as automotive sheet and extrusions, are attracting great attention. However, some inherent disadvantages of common wrought Mg alloys have limited their application, such as poor corrosion resistance, poor creep resistance and low formability. It is well known that Sn can provide thermally stable Mg₂Sn particles in the matrix of magnesium alloys. Our previous study shows that the Mg-4Zn-2Al-2Sn alloy has potential to be developed into a wrought Mg alloy. Currently, the microstructure, texture and mechanical properties of Mg-4Zn-2Al-2Sn alloy extruded at temperatures of 225, 250 and 275 ℃ have been investigated, where complete dynamic recrystallization occurred during extrusion and the average grain size was reduced to 4.4, 7.1 and 10.5 μm, respectively. The amount and morphology of the second phases were directly influenced by the extrusion temperature. Extruded at 225 ℃, irregular Mg₂Sn phase in size of 20~60 nm precipitated in the grains. With the extrusion temperature increasing to 275 ℃, Mg₂Sn of about 500 nm and micron-size Mg₃₂(Al, Zn)₄₉ precipitates were observed. The {0002} texture was formed at 225 and 250 ℃ during the extrusion. While the temperature increased to 275 ℃, due to the activation of prismatic slip system, \{10 {\displaystyle \stackrel{-}{1}} 0\} < 0002 > texture of prismatic plane parallel to extrusion direction was also observed. When compressive stress loaded along the extrusion direction, the \{10 {\displaystyle \stackrel{-}{1}} 0\} < 0002 > texture suppressed the activation of the tensile twinning \{10 {\displaystyle \stackrel{-}{1}} 2\} , which leads to a decrease of asymmetry between tension and compression.