Cooling Rate Sensitivity of RE-Containing Grain Refiner and Its Impact on the Microstructure and Mechanical Properties of A356 Alloy

The cooling rate sensitivities of AlTiB, RE and AlTiB-RE refiners were investigated using laboratory experiments and the actual industrial applications of A356 automotive wheel via low pressure die casting technology. Their impact mechanisms on the microstructure and mechanical properties of the A356 alloy were discussed. The results demonstrated that the AlTiB-RE refiner possessed most effective and synergetic refinement effects compared to the individual AlTiB or RE refiners. The AlTiB-RE refiner exhibited the least sensitivity to the cooling rate changes than the other refiners. The comprehensive properties of alloy wheel refined by the AlTiB-RE refiner were improved significantly. The tensile strength, yield strength, and elongation of wheel spoke improved by approximately 11.3%, 10.8% and 44.1%, respectively. The property difference values of the tensile strength, yield strength, and elongation in different positions of the wheel decreased from 14.8%, 31.2% and 47.7% to 8.6%, 27.1% and 30.9%, respectively.