Effect of Structure on Hot Tearing Properties of Aluminum Alloys

Hot tearing is a significant problem upon direct-chill casting of high-strength aluminum alloys. The occurrence of hot cracks is related to the thermal contraction of the solid phase and to the lack of feeding by the liquid phase during solidification. It has been identified that structure features such as grain size and amount of nonequilibrium eutectics influence both phenomena involved in hot tearing. Experimental and computer-simulation results are presented for a range of model and commercial aluminum alloys. The results are obtained both during special small-scale experiments and during industrial-scale direct-chill casting. It is shown that grain refinement reduces hot tearing susceptibility of aluminum alloys through the related decrease of the temperature of thermal contraction onset and increased permeability of the mushy zone. The effects of process parameters on hot tearing are also discussed.