The Effect of the Heat Treatment on the Dust Emission During Machining of an Al-7Si-Mg Cast Alloys

Abstract

This paper reports on the effect of artificial aging on the machinability of Al-7Si-Mg (A356) cast alloys for the as-received alloy, solution heat-treated (SHT) alloy and then aged SHT alloy at 155, 180, and 220 °C, respectively. The influence of heat treatment on the machinability of the alloys studied was considered using innovative criteria such as dust emission. The effect of various lubrication modes including dry, mist, and wet process, as well as cutting speed and feed rate, was also investigated. The results obtained from the statistically designed experiments indicate that at the same cutting conditions, the A356-T7 heat treatment generates less dust emission level compared to other various heat treatments (there is 32% less airborne swarf produced than with A356-T6). Aging at low temperature was observed to produce the greatest level of the dust emission while the aging at higher temperatures is accompanied by a reduction in the dust emission level. Fracture surface analysis using scanning electron microscope, has shown that dust emission levels were strongly dependent on the nature of the fracture surface of the alloys studied, with different heat treatments. A change in chip formation was also found to be a function of age hardening and dust emission during machining of the tested aluminum alloy. A correlation was established between the cutting speed, the feed rate, and the dust emission, which is useful for determining the conditions required for minimal dust emission.