Correlation of microstructure with mechanical properties and fracture behavior of A356-T6 aluminum alloy fabricated by expendable pattern shell casting with vacuum and low-pressure, gravity casting and lost foam casting

In the present work, a novel casting process named expendable pattern shell casting process with vacuum and low-pressure (EPSC-VL) was introduced to produce A356-T6 aluminum alloy. The correlation of microstructure with mechanical properties and fracture behavior of A356-T6 aluminum alloy was investigated. The results were then compared with lost foam casting (LFC) and gravity casting (GC) processes. Obtained results showed that the sizes of the α-Al primary phase and eutectic silicon particles as well as SDAS value of A356-T6 aluminum alloy obtained from the EPSC-VL process were smaller than that from the LFC and GC processes, and the porosity defects significantly decreased compared to the other processes, especially the LFC process. The significant improvements in microstructure and porosity level of the EPSC-VL process resulted in superior mechanical properties compared to that obtained from the other two processes. The fractographs of samples obtained with the EPSC-VL process clearly exhibited a dimple morphology, and the fracture mode was intergranular. The fracture surfaces of the GC samples exhibited a transgranular fracture mode, while, the fractographs of samples obtained with the LFC process displayed a brittle fracture mode, and the fracture path preferentially initiated at porosity defects due to its high porosity level in these samples.