拉力在铸造铝硅合金热裂形成过程中的作用(英文)

Role of tensile forces in hot tearing formation of cast Al-Si alloy

利用A356合金研究拉力在热裂的形成及其断裂行为中的作用。利用一个新型的实验装置进行相关实验研究。该实验装置能够同时测量并采集受限试样在凝固过程中施加的拉力和温度的数据。这些数据可以用来研究热裂的萌生和扩展。研究了在不同加载速度下,固相率的演变和热裂的形成之间的定量关系。由实验结果可知,施加的拉力在热裂萌生初期起着复杂的作用。在合金凝固过程中,随着固相率的不断增加,拉力会逐渐增大直至最大值,然后急剧下降,此时试样出现裂纹并在拉力的持续作用下产生断裂。对于A356合金,产生早高温下产生断裂的临界应力是0.1 MPa。由热裂纹的断口形貌可知,在凝固末期形成的晶间搭桥和液膜褶皱对热裂的形成起重要的作用。

The instrumented applied rod casting apparatus （ARCA） was developed to investigate the effects of tensile forces in the hot tearing formation of cast AI-Si alloys. The obtained data of tensile forces/temperature was used to identify hot tearing initiation and propagation and the fracture surface of samples was also investigated. The result shows that the applied tensile forces have a complex effect on load onset for the hot tearing initiation and propagation. During the casting solidification, the tensile forces are gradually increased with the increase of solid fraction. Under the action of tensile forces, there will appear hot tearing and crack propagation on the surface of the sample. When the tensile forces exceed the inherent strength of alloys, there will be fractures on the sample. As for the A356 alloy, the critical fracture stress is about 0.1 MPa. The hot tearing surface morphology shows that the remaining intergranular bridge and liquid films are thick enough to allow the formation of dendrite-tip bumps on the fracture surface.