Viability of using argon gas in investment casting of pure aluminium granules by in-situ melting

Abstract

Oxidation characteristics of pure aluminium granules during in-situ melting were studied. The granules were heated at the temperature of 850 °C, for the duration of 30 min using a high temperature muffle furnace. Experiments were conducted in two different conditions; normal air and argon atmosphere. The flow rate of argon gas was set at 0.5 l/min, 2.5 l/min and 5 l/min. Heated products were visually evaluated for geometrical and physical appearance. The heated products were characterised using field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS). Macroscopically, the Al granules failed to melt and unable to replicate the mould due to the oxidation of the granule. The Al granules experienced volumetric shrinkage and the appearance become dusty greyish. The colour of the Al granules heated in normal air and argon atmosphere were corvette blue and silver grey respectively. Argon was found to reduce the oxidation of Al granules during heating. Oxide thickness in normal air was reduced from 8.52 µm to 5.02 µm when the granules were heated in argon atmosphere at the flow rate of 5 l/min. The oxide layer formed on the Al granules surface was mainly Al2O3.