Si含量对Mg-8Al-8Zn-xSi合金组织与力学性能的影响

Effects of Si Content on Microstructure and Mechanical Properties of Mg-8Al-8Zn-xSi Alloys

采用重力铸造法制备Mg-8Al-8Zn-xSi(x=1,2,4,质量分数)镁合金。研究了不同Si含量对合金显微组织及室温和高温(150℃)力学性能的影响。结果表明:合金主要由α-Mg基体、β-Mg_(17)Al_(12)、Mg_2Si和MgZn相组成。随着Si含量的增加,Mg_2Si颗粒由汉字状逐渐转变为粗大的骨骼状。Si含量从1%增加到2%和4%时,Mg_2Si颗粒的平均尺寸由25μm分别增大到30μm和150μm;合金的硬度逐渐提高;其室温及高温抗拉强度、屈服强度和伸长率均呈现先提高后下降的趋势;室温及高温拉伸断裂形式为准解理脆性断裂。

Mg-8Al-8Zn-xSi(x =1, 2, 4, mass%) magnesium alloys were prepared by the gravity casting. The effects of Si content on microstructure and mechanical properties of the alloys at both ambient and elevated temperature(150 ℃) were investigated. The results show that the as-cast microstructure consists of α-Mg matrix, β-Mg_(17)Al_(12) phase, Mg_2Si and Mg Zn phase. The morphology of Mg_2Si particles in the Mg-8Al-8Zn-xSi alloys changes from the Chinese script type to the coarse skeleton-like with the increase of Si content. The average particles size of Chinese script type Mg_2Si increases from 25μm to 150 μm with the increase of Si content from 1% to 4%, while the hardness of the alloys increases gradually with the increase of Si content. The ultimate tensile strength, yield strength and elongation of the alloys at both ambient and elevated temperature(150 ℃) increases with the increase of Si content from 1% to 2% and then decreases when increasing Si content to 4%. The fracture of the alloys are characterized by quasi-cleavage brittle mode.