Microstructures and mechanical properties of AZ91D magnesium alloy processed by low pressure die casting
(1.National Engineering Research Center of Light Alloys Net Forming,Shanghai Jiao Tong University, Shanghai 200030, China
2.上海市上海交通大学轻合金精密成型国家工程研究中心)
2.上海市上海交通大学轻合金精密成型国家工程研究中心)
Abstract: AZ91D alloy components were cast by low pressure die casting (LPDC) process. The mechanical properties of cast components with different microstructural features (shrinkage and distribution of Mg17Al12 second phase) were investigated under as-cast states. Compared with gravity casting, AZ91D with LPDC has much coarser grain size and second phases(Mg17Al12 and Al8Mn5). The different size and distribution of Mg17Al12 phase and shrinkage correspond to different mechanical properties. The ultimate tensile strengths and elongations are mainly decided by the content and distribution of shrinkage porosity, while the yield strengths are determined by the percentage and distribution of Mg17Al12 phase. The more and finer Mg17Al12 phase in the alloy, the relatively higher the yield strengths are. In the alloy without shrinkage, the mechanical properties are mainly determined by the size and distribution of Mg17Al12 phase. The finer Mg17Al12 phase, the better the mechanical properties are. Under optimal process, the density and mechanical properties of LPDC AZ91D are improved with fine microstructures.
Key words: AZ91D; magnesium alloys; low pressure die cast; microstructure; porosity; mechanical property