冷模压铸Mg-8Gd-3Y-0.5Zr合金的组织及性能

Microstructure and mechanical properties of cold mold die-cast Mg-8Gd-3Y-0.5Zr magnesium alloy

为了开发高强度耐热压铸镁合金,采用冷模压铸工艺制备了Mg-8Gd-3Y-0.5Zr(GW83K)合金.通过光学显微镜、扫描电镜、x射线衍射及力学性能测试等手段,分析了压铸态和短时低温固溶处理状态下合金的显微组织及力学性能.结果表明:GW83K合金冷模压铸组织比较均匀,晶粒细小(平均晶粒尺寸为40～50μm),具有优良的高温瞬时力学性能.压铸GW83K合金经低温短时固溶处理(400℃×2h)后,晶粒度变化不大,组织均匀状态未发生变化,只是片层状的共晶体消失,第二相以不连续的棒状或粒状分布于晶界处,室温拉伸力学性能可达到σb=261.7MPa,σs=240.8MPa,δ5=6.0%,比压铸态合金分别提高21%,28.4%和30.4%,且高温瞬时性能也得到进一步提高.

In order to develop thermal resistant magnesium alloys with high strength, the Mg-8Gd-3Y-0. 5Zr （GW83K） alloy was prepared by cold mold die casting technology. The microstructure and mechanical properties of die-cast and solid solution treated GW83K alloys were investigated by OM, SEM, XRD and mechanical property test. The results show that the cold mold die-cast GW83K alloy has the uniform microstructure, fine grains and good high-temperature properties. Especially, the die-cast GW83K alloy subjected to low-temperature solid solution treatment has no significant variation in both grain size and uniformity of microstructure. The lamellar eutectic has disappeared and the second phases distribute at grain boundaries in either discontinuous rod shape or granule shape. The room temperature ultimate tensile strength, yield strength and elongation of the die-cast GW83K alloy subjected to solid solution treatment can reach 261.7 MPa, 240. 8 MPa and 6.0%, and increase respectively by 21%, 28.4% and 30. 4% compared with those of die-cast GW83K alloy. And the high temperature mechanical properties of die-cast GW83K-T4 alloy get further enhanced after solid solution treatment.