重力铸造Mg-5.8Sm-0.4Zn-0.3Zr合金的热处理研究

Effect of Heat Treatment on Microstructure and Mechanic Properties of Gravity Casting Mg-5.8Sm-0.4Zn-0.3Zr Magnesium Alloy

重力铸造制备了Mg-5.8Sm-0.4Zn-0.3Zr(SZ58K)镁合金,对其进行固溶处理,并绘制了时效曲线。采用X射线衍射分析(XRD)、光学金相分析(OM)、扫描电子显微分析(SEM)等手段,研究了热处理(固溶处理、时效处理)对SZ58K镁合金的显微组织和力学性能的影响。结果表明,合金的铸态组织由α-Mg基体和晶界附近的Mg41Sm5相组成;固溶处理后,第二相组织分解,晶体内部出现少量小尺寸方块状相,其主要成分为Sm;晶粒尺寸略微长大,抗拉强度和塑性大幅提高,但屈服强度无明显变化;再经过时效处理(T6)后,屈服强度大幅提高,但由于塑性剧烈下降,抗拉强度提高幅度较小。

Mg-5.8Sm-0.4Zn-0.3Zr（SZ58K） alloy was prepared by metal mold gravity casting,and the alloy prepared was treated by solid solution,and aging curve was drawn.The microstructure and mechanic properties of Mg-5.8Sm-0.4Zn-0.3Zr alloy in different heat treatment states including solid solution and ageing treatment were investigated by optical microscope（OM）,scanning electron microscope（SEM） and X-ray diffraction analysis（XRD）.The results show that the as-cast alloy consists of α-Mg matrix and Mg41Sm5 phase near the grain boundaries.After solid solution treatment,the second phase is decomposed,and small amount of square-like phase（mainly Sm） can be found in the grain with slight growth of the grain size.The change of yield strength can be ignored,while the ultimate tensile strength and elongation are remarkably increased.After aging treatment,yield strength is increased greatly,and ultimate tensile strength is increased slightly,while elongation is sharply decreased.