Influence of laser surface melting on glass formation and tribological behaviors of Zr₅₅Al₁₀Ni₅Cu₃₀ alloy

A gradient structure was synthesized on the surface of Zr ₅₅Al₁₀Ni₅Cu₃₀ alloy with high glassforming ability by laser surface melting (LSM). Along the laser incident direction, the surface remelted alloy exhibits gradient microstructure distributed in the sequence of amorphous structure, nanocrystal- reinforced amorphous matrix composite (transitional layer A), dendrites-amorphous phase composite (transitional layer B), and crystalline phases from the top surface to the substrate. The formation mechanism of this gradient structure is discussed based on the experimental results of the microstructure together with the finite volume simulation of the process of LSM treatment. The friction coefficient of the transitional layer A is ∼2.5 times lower than those of the other layers under the same sliding friction condition, and possible reasons for this phenomenon are discussed in connection with the rolling motion and material transfer mechanism. The transitional layer B exhibits the best wear resistance among all the structures studied here, which is related to the optimized ratio of microhardness to reduced Young's modulus (H/Er).