Wear Properties of Thixoformed Al-5.7Si-2Cu-0.3Mg Aluminium Alloy

Abstract

Earlier work has shown that Al-5.7Si-2Cu-0.3Mg aluminium alloy is suitable for thixoforming process. Here, the dry sliding wear behaviour of the alloy, in the as-cast and thixoformed conditions were investigated. The cooling slope technique was used to produce the alloy with globular microstructure for the thixoforming process. Both the thixoformed and cast samples were subjected to T6 heat treatments prior to the wear tests. The tests were carried out using a pin-on-disc tribometer, against a hardened M2 tool steel disc of 62 HRC at different loads, under dry sliding conditions at fixed sliding speed and sliding distance of 1 m.s–1 and 5 km respectively. The microstructural response, worn surfaces were thoroughly and carefully examined using various methods such as scanning electron microscopy, energy dispersive spectroscopy, and differential scanning calorimetry. The density of the heat treated thixoformed alloys showed significant increase in the hardness property, among others, due to its reduced porosity. Their wear test results also observed that the weight loss of materials increase with an increase in the input load and the sliding distance for all samples. However, the as-cast alloy displayed higher wear rate compared with the thixoformed alloys. In general, the wear mechanisms showed a mixture of abrasive, oxidative and delamination wear (mild wear) at low applied loads and mainly an adhesive (severe wear) at high applied loads.