论文部分内容阅读
研究了不同冷却速度下铝合金熔体中Mg2Si的生长特征。结果发现,在常规凝固条件下,当凝固速度较慢时初生Mg2Si呈现为等轴晶;随着凝固速度增加,由等轴晶转变为树枝晶,晶体尺寸有所减小,但是树枝晶明显变长;进一步增加常规条件下的凝固速度,初生Mg2Si相尺寸更加细小,但是树枝晶的长度仍然超过了200μm,并以小平面的方式生长。在大过冷度和大冷却速率的条件下,Mg2Si相生长方式却发生了转变,由小平面生长转变为非小平面生长。经过计算,发现临界转换的冷却速率为1.169×106℃/s。
The growth characteristics of Mg2Si in aluminum alloy melt at different cooling rates were studied. The results show that, under the conventional solidification conditions, the primary Mg2Si shows equiaxed grains when the solidification rate is slow; from equiaxed grains to dendrites, the size of the crystals decreases as the solidification rate increases, but the dendrite obviously changes When the solidification rate was further increased under normal conditions, the size of the primary Mg2Si phase was finer, but the dendrite length still exceeded 200μm and grew in a small plane. Under the condition of large overcooling and large cooling rate, the growth mode of Mg2Si phase has changed, from small plane growth to non-small plane growth. After calculation, we found that the critical cooling rate of transition is 1.169 × 106 ℃ / s.