通过降低浇注温度来制备半固态料坯,再将料坯重熔至半固态,最后运用高压铸造技术成型摩托车用AZ91D镁合金零件;用光学显微镜、拉伸试验机和硬度仪等研究了成型零件的显微组织和力学性能.结果表明:半固态料坯的组织由初生α-Mg相、次生α相和γ-Mg_(17)Al_(12)相共晶组织构成,降低浇注温度可使组织细化;重熔后组织由未熔的α-Mg 固熔体和部分液相转变相组成;经过半固态高压铸造成型后,零件显微组织由未熔的α-Mg相与网状分布的共晶相组成;用该工艺制备零件的力学性能受到组织缺陷和铸件内部缺陷的影响较大,需要进一步优化半固态成型工艺.
The semi-solid billet was first fabricated by decreasing pouring temperature, then remelted to semi-solid, and a AZ91D Mg alloy component for motor by high pressure casting process was at last formed. The microstructure and mechanical properties of the component were investigated by using optical microscopy, tensile tester and hardness tester. The results show that the semi-solid billet was composed of primary α-Mg phase, secondary a phase and γ-Mg_(17)Al_(12) eutectic phase. Decreasing the pouring temperature could refine the microstructure The remelted structure was composed of unmelted α-Mg solid solution and partial liquid transformation phase. After semi-solid die casting process, the microstructure was composed of α-Mg phase and net distributed eutectic phase. The effects of microstructure defects and casting internal defects on mechanical properties of the component prepared by the process were remarkable, therefore the semi-solid die casting process needed to be optimized further.
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