Effects of Ca addition on tensile properties and microstructures of hot-extruded AZ91 alloy tube
(1.辽宁省沈阳市沈阳工业大学材料科学与工程学院
2.School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110023, China
3.General Research Institute for Nonferrous Metals, Beijing 100088, China)
2.School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110023, China
3.General Research Institute for Nonferrous Metals, Beijing 100088, China)
Abstract: As-cast AZ91+XCa (X=0, 0.5%, 1.0%, 1.5%, mass fraction) magnesium alloys were extruded into tube at 380℃ with an extrusion ratio of 6:1. The tensile properties and microstructures of extruded AZ91+XCa alloy tubes were investigated. The microstructural observation indicates that Ca can obviously refine both α-Mg grains and Mg17Al12 phase of AZ91 magnesium alloy. XRD analysis shows that the microstructure of AZ91+0.5Ca alloy consists of α-Mg solid solution and Mg17Al12 phase, while AZ91+1.5Ca alloy contains additionally Al2Ca phase. The tensile experimental results show that for the AZ91 alloy, the addition of Ca has little influence on the ambient temperature tensile properties but can improve the elevated temperature tensile properties. For the extruded AZ91+XCa alloys, the elevated temperature tensile strength decreases, and elongation increases with increasing the Ca content. The improvement in elevated temperature tensile strength of the alloy can be attributed to the presence of a Ca-containing phase, which can increase the microstructural stability of the alloy at elevated temperature.
Key words: magnesium alloy; AZ91 alloy; tube extrusion; microstructural stability