铸造Al-Si合金流动性和热裂敏感性的研究现状

Research Status of Fluidity and Heat Cracking Sensitivity of Cast Al-Si Alloys

铸造Al-Si合金特别适合大型薄壁复杂结构铸件的生产。提高合金的流动性和抗热裂敏感性,对提高铸件的合格率具有重要的意义。在梳理、对比、分析铸造Al-Si合金的流动性和热裂敏感性后,得出结论:元素种类与含量对合金的流动性影响很大。合金流动性与枝晶相干点温度联系紧密,合金流动性差异可通过测量枝晶相干点来反映。利用浇注温度与枝晶相干点温度的差值来研究合金的流动性更为贴切。结合合金凝固温度区间和流动性试样最前端的晶粒形貌,能更准确地判断出合金停止流动的方式。合金元素对合金的热裂敏感性影响很大。目前,热裂纹的形成机理主要有凝固收缩补偿理论、应变理论和脆性收缩理论。

The cast Al-Si alloys are especially suitable for the production of large thin-walled complex structural castings.Improving the fluidity and heat crack resistance of the alloy is of great significance to improve the qualified rate of castings.After combing,comparing and analyzing the fluidity and thermal crack sensitivity of cast Al-Si alloy,it is concluded that the type and content of elements have great influence on the fluidity of the alloy.The alloy fluidity is closely related to the temperature of dendrite coherence point,and the difference can be reflected by measuring dendritic coherence point.It is more appropriate to study the fluidity of the alloy by using the difference between pouring temperature and dendrite coherence point temperature.Combined with the solidification temperature range of the alloy and the grain morphology at the front end of the fluidity sample,the way of flow stopping of the alloy can be judged more accurately.Alloy elements have great influence on the thermal cracking sensitivity of the alloy.At present,the mechanism of thermal crack formation is mainly solidification shrinkage compensation theory,strain theory and brittle shrinkage theory.