Effect of Severe Plastic Deformation on Mechanical Properties and Microstructure of A520 Al-Alloy Produced by Semisolid and Ordinary Casting

In the current research, the effect of severe plastic deformation by multi-directional forging (MDF) and equal channel angular pressing (ECAP) on microstructure and mechanical properties of A520 Al-alloy was investigated. The samples which produced by ordinary and semisolid casting were processed by ECAP and MDF at room temperature (RT) and high temperature. The semi-solid process improved the formability of the alloy, such that the semi-solid specimens were ECAP and MDF processed up to 3 passes at RT without cracking, while the ordinary cast specimens were cracked at the first pass of MDF and ECAP processes at RT. The micro-hardness and shear punch tests showed increase the mechanical properties of the specimens, such that 3 passes of MDF and ECAP at RT increased the hardness of specimens from 60 to 128 and 137 HV and yield strength of specimens from 128 to 208 and 255 MPa, respectively. By increasing the ECAP temperature, the effect of ECAP on improvement of mechanical properties decreased considerably. The microstructural characterization by scanning electron microscope showed that the reason of mechanical properties improvement during ECAP and MDF processes lied in the grain refinement and modification of morphology and distribution of Al3Mg2, Mg2Si and AlFe precipitates during the processes. Comparison of ECAP and MDF processes revealed that the effect of ECAP process on microstructural modification and consequently improvement of mechanical properties was higher than that of MDF process.