AlMg10合金铸造零件表面缺陷成因探析

点蚀等表面缺陷会最终导致铝合金的失效.运用金相、扫描电镜、能谱、光谱以及化学分析等多种手段,研究了AlMg10合金零件表面缺陷的形貌和成分.结果表明,该零件表面缺陷主要为表面点蚀及皮下气孔.点蚀主要是因为表层及表面中含有较多的氯、硫等元素.讨论了皮下气孔形成的机理,认为皮下气孔中的夹杂来自熔体中尺寸接近或小于某一临界尺寸的异质相质点;凹槽形核机制是皮下气孔形核的主要机制,合金熔体凝固时的收缩为气孔形核和长大提供了驱动力.

The Analysis of the Surface Defects of the AlMg10 Alloy Parts

The microstructure and chemical composition of the surface defects of AlMg10 alloy were analyzed by the means of OM, SEM, EDX, chemical analysis (CA) and ICP-AES. The results show the surface of the AlMg10 alloy contains two types of defects-pitting corrosion and subsurface blowhole. The process of the pitting corrosion was activated and accelerated by the highly contained Cl, S in the surface and the gas pore of the subsurface. The mechanism of the forming of the subsurface blowhole has also been discussed. The research shows that the concave in the non-metallic inclusions in the Al melt provides a spot for the nucleation of the subsurface blowhole. The size of the non-metallic inclusions is less than a threshold value. The driving forces for the growth of the subsurface blowhole come from the shrinkage of the solidifying melt.