Microstructure and property modifications in surface layers of a Mg-4Sm-2Al-0.5Mn alloy induced by pulsed electron beam treatments

In this work, surface modification of a Mg-4Sm-2Al-0.5Mn alloy with high current pulse electron beam (HCPEB) under different number of pulses were investigated. The evolution in microstructure, composition and phase components and properties in the surface layer before and after HCPEB treatment were characterized. It was found that the Al11Sm3 and Al2Sm phases in the surface layer were gradually dissolved during HCPEB treatment, leading to the formation of a chemical homogeneous melted layers. Besides, deformation bands were formed in the treated layer due to the thermal stress generated during treatment. After 15 pulses treatment, the surface hardness increases to the maximum value of about 62.2 HV, about 61.2% higher than that of the untreated state. Electrochemical results show that the 15 pulses treated sample presents the best corrosion resistance in the 3.5wt% NaCl water solution by showing the highest corrosion potential (Ecorr) of -1.339VSEC and the lowest corrosion current density (Icorr) of 1.48 × 10−6 A·cm−2. The results prove that the surface properties of the Mg-4Sm-2Al-0.5Mn alloy can be significantly improved by the HCPEB treatments under proper conditions.