ABSTRACT

In the automotive industry, mechanical grinding is employed at finishing line rectification to remove defects left over from upstream, which may also result in microstructure modification within the near-surface region of the work piece and, consequently, affects its corrosion performance. The present work investigates the influence of mechanical grinding on the microstructure modification and corrosion behaviour of Al–Si–Mg (A356) alloy castings in order to advance the understanding of potential corrosion issues. It is found that a near-surface deformed layer with a maximum thickness of 3 μm, characterised by ultrafine equiaxed grains of 50–150 nm diameter, is introduced by the grinding process on α-aluminium matrix. The near-surface deformed layer has a significant impact on the corrosion behaviour of the alloy; specifically, preferential dissolution of the near-surface deformed layer occurs when exposed to NaCl solution, together with trenching of the aluminium matrix around the eutectic silicon particles.

摘要

在汽车工业中，在精加工线整改中采用机械磨削来去除上游遗留的缺陷，这也可能导致工件近表面区域内的微观结构发生改变，从而影响其耐腐蚀性能。目前的工作研究了机械磨削对 Al-Si-Mg (A356) 合金铸件的微观结构改性和腐蚀行为的影响，以促进对潜在腐蚀问题的理解。研究发现，在α-铝基体上通过研磨工艺引入了最大厚度为3 μm的近表面变形层，其特征在于直径为50-150 nm的超细等轴晶粒。近表面变形层对合金的腐蚀行为有显着影响；具体来说，