Effect of laser-shock peening on the structure and nano-mechanical behavior of a Ti-based metallic glass

As a versatile and nondestructive method, laser-shock peening (LSP) has been extensively utilized to improve the mechanical properties of metallic components. Nevertheless, the underlying mechanism for the LSP-induced structure transformation remains unclear. In this study, the structure and nano-mechanical behaviors of a Ti₄₀Zr₂₅Ni₃Cu₁₂Be₂₀ bulk metallic glass (BMG) were investigated before and after LSP processing. The LSP-treated BMG sample remains its amorphous structure. As the laser-beam energy increases, there is a reduction in the local order extent of LSP-treated Ti₄₀Zr₂₅Ni₃Cu₁₂Be₂₀ BMGs samples, i.e., an increase in the free-volume contents. A higher free-volume content caused a greater shear-band density for the studied BMG samples, causing a lower nano-hardness. Besides, there exists a gradient in nano-hardness along the LSP direction inside the sample, the nano-hardness increases along the LSP direction (gradually approaching the matrix hardness). This gradient effect can be attributed to the gradual decay of the shock-wave pressure with increasing the depth.