冷却过程对AZ61镁合金凝固组织的影响

将AZ61镁合金液态凝固过程分为高温熔体和凝固两个阶段,研究各阶段冷却速率对铸态组织的影响,不同冷速下铸态合金枝晶间距的变化及其对显微硬度的影响。结果表明:在高温熔体阶段随着冷却速率从0.65℃/s增加到15.9℃/s,枝晶组织不断细化且尺寸更均匀,一次枝晶间距从230μm逐渐减小到80μm,二次枝晶间距从12.8μm逐渐减小到9.2μm;凝固阶段在7.8℃/s至23.0℃/s不同冷却速率下,一次枝晶间距从105μm逐渐减小到73μm,二次枝晶间距从10.6μm逐渐减小到8.8μm。两个阶段显微硬度值随冷却速率增大都呈增高趋势。相对于凝固阶段,高温熔体阶段的冷却速率变化对铸态凝固组织的影响更显著。

Effects of Cooling Process on Microstructure of As-cast AZ61 Magnesium Alloy

The liquid solidification process of AZ61 magnesium alloy was divided into two stages of high-temperature melt and solidification.The effects of different cooling rates of each stage on the cast microstructure and the variations of dendrite spacing on the microhardness were investigated.The results show that at the high-temperature melt stage,when the cooling rate increases from 0.65℃/s to 15.9℃/s,the dendrite microstructure is continuously refined and the size becomes more uniform.The primary dendrite is decreased from 230μm to 80μm and the secondary dendrite spacing is decreased from 12.8μm to 9.2μm.At the solidification stage,when the cooling rate increases from 7.8℃/s to 23.0℃/s,the primary dendrite spacing is decreased from 105μm to 73μm and the secondary dendrite spacing is decreased from 10.6μm to 8.8μm.In the two stages,the microhardness value presents increasing trend with the increase of cooling rate.By comparison,the change of cooling rate has a larger impact on the as-cast microstructure of high-temperature melt stage than that the solidification stage.