真空增压铸造对Mg-Y-Nd-Gd-Zn-Zr合金工艺性能和力学性能的影响

目的通过真空增压工艺改善Mg-Y-Nd-Gd-Zn-Zr合金的铸造性能和力学性能。方法采用螺旋法、热裂环法、线收缩率测试方法,分别测试了不同真空度、浇注温度、凝固压力下合金的流动性、热裂倾向和收缩率。采用万能拉伸机测试合金的力学性能,采用金相显微镜观察合金的显微组织,采用截线法测量平均晶粒尺寸。结果重力下Mg-Y-Nd-Gd-Zn-Zr合金的螺旋长度为240~270 mm,裂环宽度为10~15 mm;真空下的螺旋长度为245~330 mm,裂环宽度为7.5~12.5 mm;凝固压力从0.2 MPa提升至0.8 MPa,合金的抗拉强度从320 MPa提升至335 MPa,断后伸长率从4.5%提升至6.0%。结论提高真空度、浇注温度,可显著提升合金的充型能力;提高凝固压力、降低浇注温度,可明显降低合金的热裂倾向;凝固压力越高、真空压力转换时间越短,合金的组织越致密,力学性能越高。

Effects of Vacuum Casting and Solidification under Pressure on Process Performance and Mechanical Properties of Mg-Y-Nd-Gd-Zn-Zr Alloy

The paper aims to improve the casting process performance and mechanical properties of Mg-Y-Nd-Gd-Zn-Zr alloy by vacuum casting and solidification under pressure. The mobility, hot cracking tendency and shrinkage ratio of the alloy under different vacuum degree, pouring temperature and solidification pressure were tested by spiral method, hot cracking method and line shrinkage test method, respectively. The mechanical properties of the alloy were tested by a universal testing machine. The microstructures were observed by a metallographic microscope, and the average grain size was measured by truncation. The spiral length of Mg-Y-Nd-Gd-Zn-Zr alloy was 240~270 mm, the width of hot cracking was 10~15 mm by gravity casting; and the spiral length was 245~330 mm, the width of hot cracking was 7.5~12.5 mm by vacuum casting. The solidification pressure increased from 0.2 MPa to 0.8 MPa, the tensile strength increased from 320 MPa to 335 MPa, and the elongation increased from 4.5% to 6.0%. Increasing the vacuum degree and pouring temperature can improve the filling properties. Increasing the pouring pressure and reducing the pouring temperature can significantly reduce the hot cracking tendency. The higher the solidification pressure, the shorter the vacuum pressure conversion time, the denser the microstructures and the higher the mechanical properties.