保温参数对A356铝合金半固态组织的影响

Effects of Different Holding Parameters on Water Quenched Microstructure of Aluminium Alloy A356Semi-solid Slurry

采用自孕育法制备A356铝合金半固态浆料,对比分析了半固态金属型铸造与传统金属型铸造的组织,研究了不同保温时间及保温温度对A356半固态浆料水淬组织的影响。结果表明,A356铝合金采用自孕育法进行半固态流变铸造可获得初生相分布均匀的非枝晶组织;A356半固态浆料在保温3min时初生颗粒的形状因子最接近于1,而且颗粒平均尺寸相对较小,因此,保温3min的组织为较理想的流变成形组织;保温温度的高低直接影响最终浆料固相率的高低。固相率过高（50%以上）,初生颗粒的合并现象严重,使组织恶化;固相率过低（15%以下）,浆料接近全液态,达不到半固态成形利于补缩的效果。适合A356合金的半固态保温温度为600~610℃。

Semi-solid slurry of aluminium alloy A356 was prepared by self-inoculation method（SIM）.The difference of microstructure of alloy prepared by semi-solid metal casting and traditional permanent mold casting was analyzed comparatively,and effects of holding time and temperature on water-quenched microstructure of A356semi-solid slurry were described.The results indicate that the uniform primary particles with non-dendrite structure in A356 aluminium alloy can be observed by semi-solid rheological casting with SIM.The shape factor of primary particles reaches or nearby 1,and average grain size is relatively fine with the slurry isothermally holding for 3min.Therefore,an ideal rheological microstructure can be obtained with the slurry holding for 3 min.The solid fraction directly depends on pouring temperature,where at high solid fraction（more than 50%）,serious mergence of primary particles can result in the structure worse.On the contrary,it is hard to get ideal feeding effect during semi-solid processing at low solid fraction（less than 15%）.The suitable holding temperature of semi-solid treatment for aluminium alloy A356 is in range of 600 ℃~610 ℃。