Surface modification of Mg67–Zn30–Y3 quasicrystal alloy by high current pulsed electron beam

The HCPEB (high current pulsed electron beam) irradiation gives rise to rapid heating, melting and cooling of material surfaces, thereby improving surface properties of materials. In this paper, the surfaces of a Mg67Zn30Y3 quasicrystal alloy (Zn 50.86 wt.%, Y 7.02 wt.%, Mg balance) were bombarded by HCPEB. The surface microstructure variations of the Mg67Zn30Y3 alloy before and after HCPEB treatment were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that the initial structure of the Mg67Zn30Y3 alloy consists of matrix Mg7Zn3, rich Mg phase (α-Mg) and quasicrystal Mg3Zn6Y. Under multiple HCPEB treatments, the phase boundaries become indistinct. The chemical composition of the surface layer tends to be a homogeneous distribution due to interdiffusion of alloying elements. Mg largely dissolved in the matrix by analyzing XRD patterns, causing the formation of supersaturated solid solution in surface layer. Besides, a nano-structured quasicrystal layer (grain size of 10–30 nm) is obtained after HCPEB treatment. By wear tests, the wear resistance of the HCPEB-treated samples is improved by a factor of 1.2 compared with that of the initial sample and the main reason can be attributed to the formation of a metastable structure during the HCPEB process.