冷却速率对Al-Si-Mg合金次生相形成的影响

Effect of Cooling Rate on Secondary Phase Formation of Al-Si-Mg Alloys

铝合金铸件微观组织在铸造过程中受冷却速率影响很大。本文选用5、10、15℃/min的冷却速率进行Al-Si-Mg合金凝固试验,研究冷却速率对不同成分的Al-Si-Mg合金次生相析出的影响。结果表明冷却速率的提高能使α-Al的初晶一次和二次枝晶间距降低,有利于细化各次生相尺寸,共晶组织分布更弥散,使各凝固反应的温度区间扩大并向低温方向移动,初晶凝固受到抑制。多元共晶反应受到抑制且冷速过大时消失,多元共晶中Mg2Si相的析出及Al-Mg2Si共晶树状形貌的形成受到阻碍。

The microstructure of aluminum alloy castings is greatly affected by the cooling rate during casting. The Al-Si-Mg alloy solidification test was carried out at the cooling rate of 5,10,15℃/min. The effect of cooling rate on the secondary phase precipitate of Al-Si-Mg alloys with different compositions was studied. The results show that as the cooling rate increases, the primary and secondary dendrite spacing of the α-Al is reduced, the size of each secondary phase is refined,the eutectic structure distribution is more dispersed, the temperature range of each solidification reaction is expanded and moved to the low temperature direction, and the primary cry stal solidification is inhibited. The multicrystalline reaction is inhibited and disappears when the cooling rate is too high. The precipitation of Mg2 Si phase and the formation of Al-Mg2 Si eutectic dendrite morphology are hindered.