Correlation of microstructure with mechanical properties and fracture toughness of A356 aluminum alloys fabricated by low-pressure-casting, rheo-casting, and casting–forging processes

Correlation of microstructure with mechanical properties and fracture toughness of three cast A356 aluminum alloys fabricated by low-pressure-casting, rheo-casting, and casting–forging was investigated in this study. Microfracture observation results showed that eutectic Si particles were cracked first, but that the aluminum matrix played a role in blocking crack propagation. Tensile properties and fracture toughness of the cast-forged alloy were superior to those of the low-pressure-cast or rheo-cast alloy. These results were interpreted by a simple fracture initiation model based on the basic assumption that crack extension initiated at a certain critical strain developed over some microstructurally significant distance.