EFFECT OF EQUAL CHANNEL ANGULAR PRESSING ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF A356 ALLOY

摘要

This work investigated the effect of equal channel angular pressing (ECAP) on the microstructure and mechanical properties of non-dendritic A356 alloy. This alloy was casted by cooling slope casting in order to produce a globular microstructure feedstock for ECAP process. After that, ECAP process was performed using 120° of die angle via route A for 2 passes at room temperature. The microstructure of the processed alloys was observed under an optical microscope (OM) and scanning electron microscope (SEM) whereas the mechanical properties of the alloy were validated using Vickers hardness test and tensile test. Microstructure observation showed that after 2 passes, the grain size was obviously refined to 35 μm from 75 μm in the as-cast sample. The mechanical properties of the alloy were ultimately improved in ECAP sample. The hardness of the ECAP sample increased as high as 77.6 HV as compared to the as-cast alloy which was 42.3 HV. The ultimate tensile strength also increased from 105 MPa to 237 MPa after 2 passes deformation. It was also discovered that the distribution of α-Al and eutectic phases were more homogeneous at the ECAP sample than using non-dendritic structure feedstock.