浇注温度和缸体温度对AZ91D镁合金流变注射成形件组织及力学性能的影响

摘要

介绍一种先进的集金属熔化、储存、浆料制备、浆料输送和注射成形于一体的流变注射成形机,并使用该设备生产一批AZ91D镁合金流变注射成形件.研究浇注温度和缸体温度对AZ91D镁合金流变注射成形件组织和力学性能的影响规律.结果表明,流变注射成形工艺可以成功获得初生 α-Mg颗粒细小、圆整、均匀分布于基体组织中的AZ91D镁合金成形件.随着浇注温度的下降,初生 α-Mg形貌由粗大的蔷薇状逐渐转变为细球状.随着缸体温度的降低,初生 α-Mg颗粒的尺寸先下降,之后基本保持不变,其球形度和固相率不断提高.同时,适当地降低浇注温度或缸体温度可以细化 α-Mg颗粒和降低孔隙率,这有助于流变注射成形件力学性能的提高.另外,AZ91D镁合金流变注射成形件在力学性能上优于触变注射成形、流变压铸成形和高压铸造.与高压铸造相比, AZ91D镁合金流变注射成形件的抗拉强度、屈服强度和伸长率分别提高了27.8%、15.7%和121%.%An advanced rheomoulder, which is a device in the integration of melting metal, storage, slurry preparation, transportation and injection forming, was introduced and used to manufacture rheomoulding AZ91D alloy. Effects of pouring temperature and cylinder temperature on microstructures and mechanical properties of rheomoulding AZ91D alloy were investigated. The results show that the process can obtain such rheomoulding AZ91D in which primary α-Mg particles are fine, spherical and uniformly distributed in the matrix. With the decrease of pouring temperature, the morphology of primary α-Mg particles changes from coarse rosette-like to fine spherical shape gradually. As the cylinder temperature decreases, the average size of primary α-Mg particles decreases firstly and then substantially maintains stable while the sphericity and solid fraction increase continuously. Also, decreasing pouring temperature or cylinder temperature properly contributes to improving mechanical properties of rheomoulding AZ91D for the refinement of α-Mg particles and the decrease of porosity fraction. Furthermore, rheomoulding AZ91D performs much better than thixomoulding, rheo-diecasting and high pressure die-casting (HPDC) in terms of mechanical properties. Compared with HPDC, the tensile strength, yield strength and elongation are increased by 27.8%, 15.7% and 121%, respectively.