A Study of Structure and Morphology of Bulk Metallic Glasses after Laser Beam Treatment

Recently, the Zr-based bulk metallic glasses (BMGs) have attracted attention because of their good glass-forming ability and excellent mechanical properties. The amorphous structure is thermodynamically unstable, and it tends to change into an equilibrium crystalline state. The objective of this work is to test the influence of the laser beam on the surface structure and morphology of BMGs with zirconium matrix. The material for the examination was Zr₅₅Cu₃₀Ni₅Al₁₀ alloy obtained by high-pressure copper mold casting method in the form of a plate in specified dimensions. In this paper, irradiation with single impulse and laser beam welding emitted in a pulsed mode which consists of a series of overlapping point interactions were used. Different parameters of the laser beam were employed. Microscopic observations proved that after laser treatment amorphous-crystalline structure appears in the heat-affected zone (HAZ). High-resolution transmission electron microscopy analysis of irradiated metallic glass showed that small amount of crystalline Zr₂Ni-type phase was produced in the HAZ, whereas in the fusion zone and parent material amorphous structure appears. What is more, it has been observed that the higher laser beam frequency and energy the more weld penetration takes the shape of an ellipse.