热处理对AZ80镁合金结构及性能的影响

EFFECT OF HEAT TREATMENT ON MICROSTRUCTURE AND PROPERTIES OF AZ80 MAGNESIUM ALLOY

利用环境扫描电镜(ESEM)和透射电镜(TEM)研究了时效温度对AZ80镁合金析出相的影响,测定了析出相/ 基体的位向关系,分析了不同析出相的析出机理及其对合金性能的影响.实验中观察到β-Mg17Al12析出相的一种新的析出方式一颗粒状β相沿晶界及孪晶处形核、生长. AZ80镁合金高温(310℃)时效时,析出相为连续析出,呈菱形片状或颗粒状. 其中前者在晶内均匀形核生长,与基体的基面平行,对合金性能有一定强化作用;而后者分布于晶界,它的出现大大降低了合金性能.时效温度降低(<250℃),将出现不连续析出相,呈片层状,其片层与基体基面平行或垂直,在晶界形核并向晶内生长,随着不连续析出相的生长,将推动晶界向前移动,不连续析出相对合金的性能强化效果较大.

The effect of aging temperature on precipitates in AZ80 magnesium alloy was studied by using environmental scanning electron microscope （ESEM） and transmission electron microscope （TEM）. The precipitate/matrix orientation relationships （ORs） were measured, the precipitation mech- anism was analyzed and the effect of precipitates on properties of alloy was tested. A new precipitated way of granular β-Mg17Al12 phase was found in aged alloy, which was granular and nucleated at grain boundaries （GBs） and twin boundaries. Plate-like or graunlar-like β-Mg17Al12 precipitated continuously in the alloy aged at higher temperature （310℃）. The plates were parallel to the basal plane of matrix, nucleated and grew homogeneously in grains, and had little effect on properties of alloy. Whereas the granular β-phase was harmful for the alloy property. The discontinuous precipitation of β-phase occurred at lower aged temperature （〈250℃）, which was lamellar structure parallel or perpendicular to the basal plane of matrix, nucleated at grain boundaries and grew into grains. The grain boundaries moved into the grains with the growth of these discontinuous precipitates. The alloy was strengthened by the discontinuous precipitates evidently.