Investigation of Oxidation Behaviors of Al-Mg Alloys with a Grain Refiner at High Temperature

Abstract

Studies to investigate the oxidation behavior of Al–Mg alloys with Al-5 mass%Ti-1 mass%B master alloy as a grain refiner at high temperature were conducted. The Scheil-Gulliver cooling calculation showed that, in 0.2 mass%Ti-inoculated alloy, TiAl3 was formed before the primary Al formation, which may act as a grain refiner. The optical microstructures showed a significant grain refinement after the addition of 0.2 mass%Ti using Al-5 mass%Ti-1 mass%B master alloy. Moreover, the oxidized cross-sections, throughout the oxidation time, show coarse and dark areas (regarded as oxide clusters), which were nonuniformly distributed in the matrix after oxidation at 500 °C under an ambient atmosphere. In addition, an accumulation of oxygen by diffusion for a long duration led to the growth of blisters after 50 h. At the oxidation temperature, Mg3Ti2Al18 was found to be only stable Ti-containing phase and possibly formed MgO by the interaction with the diffused oxygen.