Mechanical properties of Al-9Si-0.6Mg-0.1Sr alloy processed by successive hot and cold multi-directional forging

Abstract

In this study, the effect of successive hot and cold multi-directional forging (MDF) on the mechanical properties of the Al-9Si-0.6Mg-0.1Sr alloy was explored. The alloy was first homogenized and then forged at 200°C from 3 to 15 passes. After each three passes of hot forging, the samples were then cold forged up to three passes at room temperature. The microstructural examinations were carried out with X-ray diffraction technique and scanning electron microscopy equipped with energy-dispersive spectroscopy while mechanical properties were determined by tensile, compression and hardness tests. The hard particles were fragmented and began to distribute homogeneously into the matrix with increasing pass number of hot MDF. The yield, tensile and compressive strengths of the alloy reached to their maximum values at three passes of hot MDF along with hardness, above which they decreased, while its ductility exhibited a reverse trend. The cold MDF significantly increased the mechanical properties of initially hot MDFed samples. The nine passes in hot MDF were determined as the optimum pass number for obtaining the highest yield and tensile strength after cold MDF. These findings were evaluated according to dislocation strengthening, recrystallization and morphology of hard particles.