Corrosion and Mechanical properties of Thixoformed A357 alloy

摘要

The mechanical and corrosion properties of thixoformed A357 alloys were examined with different reheating temperatures, and the results were compared with those of permanent mold cast A357 alloys. It was found that the thixoforming process significantly improved the mechanical properties (i.e., tensile elongation, impact energy and resistance to fatigue crack propagation) and the corrosion resistance of A357 alloys. A 380 percent increase in tensile elongation and a 120 percent increase in impact energy were, for example, observed with thixoforming process of A357 alloy in the as-fabricated condition, as compared to the PMC counterparts. The impact energy was extremely sensitive to reheating temperature due to the coarsening of eutectic Si particles. The resistance to fatigue crack propagation for the thixoformed alloy was also much higher than that of permanent mold cast counterpart in the as-fabricated condition. The resistance to both general corrosion and stress corrosion cracking was also greatly improved with thixoforming process. The present observations strongly suggest that the enhancement with thixoforming A357 alloy is largely associated with the size and shape of eutectic Si particles.