AZ91镁合金的形变热处理

Thermomechanical Treatment of AZ91 Magnesium Alloy

用金相显微镜、扫描电镜等分析手段及力学性能测试,研究了形变热处理对AZ91合金组织及力学性能的影响。结果表明,AZ91镁合金拉伸变形主要是以孪生的方式进行。拉伸变形后的合金经时效处理时,β-Mg17Al12首先在孪晶内及孪晶界处弥散析出,随着时效时间的延长,析出物的量不断增加。当孪晶内析出物的量达到一定值时,在晶界处出现了非连续的片层状β-Mg17Al12相,晶内也出现了少量的连续析出的β-Mg17Al12相。未发生变形的AZ91镁合金时效处理时,β-Mg17Al12相仅在晶界处以非连续的方式呈片层状形式析出。AZ91镁合金变形试样经时效处理后,其室温抗拉强度均高于经过相同工艺时效处理后的未变形试样,且当时效时间为12 h时达到最大值。

By using OPM, SEM and mechanical tests methods, the effect of thermomechanical treatment on the microstructure and mechanical properties for AZ91 magnesium was studied. The results show that the twinning is the main deformation mode during tensile deformation. After tensile deformation and aging treatment, there are some β-Mg17Al12 phase precipitated from twins and twin boundary the in the alloy. With the prolonging of aging time, the precipitate phase increases. When the amount of precipitated phase in twins reaches a critical value, the discontinued lamellar β-Mg17Al12 occurs in gain boundary. At the same time, a small amount ofβ-Mg17Al12 phase occurred by continuous precipitation in grain. After aging treatment in AZ91 alloy with no deformation, the β-Mg17Al12 phase only precipitates on the grain boundary by the discontinuous lamellar mode.After thermomechanical treatment and aging treatment, the tensile strength at room temperature is higher than that of no deformation. When the aging time is 12 h, the tensile strength reaches the maximum value.