Study of hot tearing of A206 aluminum alloy using Instrumented Constrained T-shaped Casting method

Abstract

The hot tearing susceptibility of A206 aluminum alloy was investigated using Instrumented Constrained T-shaped Casting method and the effect of the casting temperature on hot tearing was studied. The Instrumented Constrained T-shaped Casting apparatus enabled real-time measurements of the contraction load developed in the casting and the temperature variations during solidification as a function of time. Critical temperatures and points during solidification of the castings were extracted from these data. The contraction load developed at the coalescence point of the castings was identified as a comparative criterion for predicting the hot tearing susceptibility of the alloys which could be utilized even when no visual tearing had occurred. The results showed that hot tearing susceptibility increased with the casting temperature. This was associated with reduced cooling rate, increased solute segregation and more localized hot spot formation at the T-junction area. Increase in the casting temperature also increased the grain size which may in turn have affected the initiation of the hot tears. The visual observations were further validated with radiographic tests.