Surface modification of sub-eutectic silumin by a pulsed electron beam

Abstract

The research has pointed out that the electron-beam irradiation induces the formation of an approximately 90 μm thick surface layer, where primary inclusions dissolve. There are two defect sub-structure types in the irradiated samples: cells and columns. An important outcome to emerge from the study is that the fracture of an irradiated sample occurs at greater (by ≈7 %) applied stress and higher (by ≈13 %) plastic strain than in the as cast silumin. Stress-strain curves of samples under study were presented in the coordinates s-e0.33. As a result, straight-line segments were detected, which characterize different stages of strain hardening in the material. Strain-stress curves of untreated samples in the coordinates s(e0.33) show three straight-line segments referring to three stages of hardening. Stress-strain curves of irradiated samples also demonstrate three stages of hardening; however, two additional strain hardening stages of silumin (intermediate and before-fracture) are found out. The study suggests disappearing of local compression zones in both samples but at various values of strain, moreover, local zones in irradiated samples are not registered at greater strain. In this context it is concluded that the irradiation of АК5М2 alloy samples contributes to the stabilization of local micro-zones with compressive strain.