低温挤压Mg-4Zn-2Al-2Sn合金的组织与力学性能研究  

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Mg-4Zn-2Al-2Sn ALLOYS EXTRUDED AT LOW TEMPERATURES

作　　者：赵东清[1,2] 周吉学[2] 刘运腾[2] 董旭光[1] 王晶[1] 杨院生[1,2] 

机构地区：[1]中国科学院金属研究所,沈阳110016 [2]山东省科学院新材料研究所,济南250014

出　　处：《金属学报》2014年第1期41-48,共8页Acta Metallurgica Sinica

基　　金：国家支撑计划项目2011BAE22B01-1;国家国际科技合作计划项目2011DFA50903;山东省自然科学基金项目ZR2010EQ021资助~~

摘　　要：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.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 dis- advantages 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-2A1-2Sn alloy has potential to be devel- oped 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 re- crystallization 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. Ex- truded at 225 ℃, irregular Mg2Sn phase in size of 20-60 nm precipitated in the grains. With the extrusion tempera- ture increasing to 275 ℃, Mg2Sn of about 500 nm and micron-size Mg32（A1, Zn）49 precipitates were observed. The {0002} texture was formed at 225 and 250 ~C during the extrusion. While the temperature increased to 275 ~C, due to the activation of prismatic slip system, { 10]-0} 〈0002〉 texture of prismatic plane parallel to extrusion direc- tion was also observed. When compressive stress loaded along the extrusion direction, the {10]-0} 〈0002〉 texture suppressed the activation of the tensile twinning { 1012} 〈1011〉, which leads to a decrease of asymmetry between tension and compression.

关 键 词：镁合金 低温挤压 组织 力学性能 

分 类 号：TG146.2[一般工业技术—材料科学与工程]