In situ investigation of the evolution of shear transformation zones with different elastic tensile strains in metallic glass

Abstract

Shear transformation zones are usually thought as the fundamental unit characterizing microscopic atomic rearrangement motion during deformation in amorphous materials and the corresponding evolution process determines the macroscopic mechanical behaviors. However, the evolution process of shear transformation zones under tensile loading are difficult to be experimentally detected. Here, one in-situ tensile platform coupled with nanoindenter was introduced to conduct a series of nanoscale continuous loading and creep tests on Cu50Zr50 metallic glass film under different pre-tensile strains within the elastic deformation region. The effects of loading rate and pre-tensile strain on the continuous loading and creep behaviors were systematically investigated. Moreover, the corresponding shear transformation zone volume, the activation volume and the relaxation time spectrum during tensile deformation were determined based on the Cooperative Shearing model and Maxwell-Voigt model. It was found that both of the shear transformation zone volume, activation volume and the peak intensity for the relaxation time spectrum increase with pre-tensile strain. Finally, one scheme is proposed to illustrate the microscopic mechanism for the evolution of shear transformation zones during tensile deformation. The current study offers one effective experimental strategy to in-situ investigate the mechanical behaviors and to reveal microscopic deformation mechanism in amorphous materials.