ADC14挤压铸造件中Si偏析的原因分析

Analysis of the Segregation of Si Particles in ADC14 Squeeze Castings

分析了ADC14挤压铸造件的微观组织和力学性能。结果表明,在试样金相组织中均发现有孔洞缺陷的存在,且孔洞数量随着离内浇口距离的增加而增大;在试样标距段心部位置存在着严重的初生Si富集和偏析,是导致试验挤压铸造ADC14铝合金力学性能下降的主要原因。Si的偏析原因为,在挤压力和快速冷却的共同作用下,凝固初期铸件边缘处发生非平衡结晶而获得大量初生α-Al相,使得残留液相Si含量富集,在其后的凝固过程中,挤压力的强制补缩流动作用加剧了标距段心部的Si元素和粒子的正偏析。

The microstructure and mechanical properties of ADC14 squeeze castings were analyzed. It is found that there exist porosities in the different location, and the porosity contents are increased with increasing in distance from the ingate. In addition, serious enrichment and segregation of the primary Si particles appeared in the central of the casting gauge parts, which should be responsible for the inferior mechanical properties. In the early solidification, non-equilibrium crystallization happens and a large number of primary phase a-Al is formed at the casting surface as a result of squeezing force and high cooling rate, resulting in Si enrichment in the residual liquid. Furthermore, during following solidifica- tion periods, the forced feeding flow resulted from squeeze force made the Si riched liquid flow to the center of the gauge part, which are responsible for the serious positive segregation of Si contents and particles there.