Identification of rejuvenation and relaxation regions in a Zr-based metallic glass induced by laser shock peening

Abstract

In this paper, laser shock peening (LSP) treatment was performed on Zr35Ti30Cu10Ni5Be20 bulk metallic glass (BMG) and the effects of induced energy on the characteristics of glassy structure were evaluated. The high resolution atomic force microscopy (AFM) and nanoindentation tests were carried out to characterize the nanoscale heterogeneity and micromechanical properties in the depth of material. According to the results, the surface of material showed a high heterogeneous structure, which was the sign of structural rejuvenation. However, with the move into the depth of material, the nanoscale heterogeneity decreased and eventually a relaxed region with the minimum heterogeneity was found in the 1.5–2 mm depth of BMG sample. Passing the relaxed region, again the nanoscale heterogeneity similar to the as-cast sample was observed. The nanoindentation results also confirmed the AFM outcomes. It is suggested that the relaxed region at the neighbor of rejuvenated region is due to the satisfaction of elastic adaptability which is resulted by the nanoscale shear events and the induced stress.

Keywords

• Bulk metallic glass
• Rejuvenation
• Relaxation
• Laser energy