Corrosion Improvement and Microstructure Evaluation of SEM-Solid A356 Alloy by Ecap Process

Abstract

Al-Si is a casting alloy developed mostly for automobile and aircraft engine industries. This research presents a study related to the semi solid casting of Al-Si A356 alloy produced by cooling slope known as thixoforming process. The sample has then undergone T6 heat treatment. The grain refinement was achieved suitable for thixoforming by Severe Plastic Deformation (SPD) technique through Equal-Channel Angular Pressing (ECAP). The ECAP was conducted at room temperature in which a 10 mm rod was pressed through a constrained channel of a die that was bent abruptly close to 120°. The coarse α-Al phase and silicon particles changes into a globular shape after thixoforming process and T6 heat treatment. The ECAP processing through route A leads to particle refinement after one pass and further refined with an average particle size of 41.2μm after two pass pressing. The potentiodynamic test showed that the corrosion rate reduced to 0.0024 mmpy after two passes of ECAP processing. It confirms that particle refinement through ECAP processing leads to significant enhancement of corrosion resistance in A356 alloy.