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分别向AZ81镁合金熔液中加入0.5%,1.0%,1.5%(质量分数)的Pb,压铸成型并进行时效热处理,然后对其微观组织和180℃拉伸性能进行了研究。结果显示:Pb对压铸态AZ81的微观组织有一定的晶粒细化作用,且随着Pb加入量的增加,晶粒细化作用有一定的增加趋势;Pb主要以固溶形式存在于压铸态AZ81镁合金的α-Mg基体和β-Mg17Al12相中;时效后,Pb在压铸AZ81镁合金中依然主要以固溶形式存在,在α-Mg晶内和晶界上均有Mg17Al12相析出,Pb可在一定程度上抑制晶界上的不连续析出并促进晶内连续析出;180℃拉伸结果显示,随着Pb加入量的增多,各成分未时效试样的抗拉强度变化幅度不大,含Pb时效态试样中温抗拉强度随Pb含量增加呈上升趋势,最高平均强度为181 MPa,含Pb试样时效态抗拉强度比同成分未时效态均有所提高;各试样时效态屈服强度均比未时效态高;Pb元素和时效热处理均使压铸AZ81镁合金延伸率下降;时效使AZ81镁合金倾向于脆性断裂,塑性下降。
The Pb, 0.5%, 1.0% and 1.5% (mass fraction) Pb were added to the AZ81 magnesium alloy melt respectively, and then were subjected to die casting and aging heat treatment. The microstructure and tensile properties at 180 ℃ were investigated. The results show that Pb has a grain refining effect on the microstructure of the as-cast AZ81. With the addition of Pb, the grain refinement tends to increase. Pb mainly exists in the as-cast state AZ81 magnesium alloy and β-Mg17Al12 phase. After aging, Pb still exists in solid solution in the die-cast AZ81 magnesium alloy. In the α-Mg crystal and the grain boundary, Mg17Al12 phase precipitates and Pb Which can inhibit the discontinuous precipitation on the grain boundaries and promote the continuous precipitation in the grain to a certain extent. The tensile test at 180 ℃ shows that with the increase of the amount of Pb, the tensile strength of the non-aged samples varies little, The tensile strength at elevated temperatures of Pb-containing specimens increased with the increase of Pb content, and the highest average strength was 181 MPa. The tensile strength of Pb-containing specimens was higher than that of non-aging specimens with the same composition. The yield strength of AZ81 magnesium alloy is higher than that of non-aging steel. The elongation of AZ81 magnesium alloy is decreased by both Pb and aging heat treatment. The aging of AZ81 magnesium alloy tends to brittle fracture and plasticity decreases.