PROBING INTO THE CREEP MECHANISM OF AMORPHOUS ALLOY BASED ON QUASI-POINT THEORY

As a typical multi-body interaction and non-equilibrium system, how to clarify the deformation mechanism under multi-field coupling stimuli and then establish the intrinsic correlation among the deformation behavior, flow characteristics and microstructure evolution of amorphous alloys keep the fundamental topic. In the current work, a prototypical La_56.16Ce_14.04Ni_19.8Al₁₀ amorphous alloy which shows a pronounced slow \;\beta relaxation process was selected as the model system. Series of creep experiments of the amorphous alloy over wide temperature and stress range were carried out. Evolution of creep compliance J , quasi steady-state strain rate \dot\varepsilon _s , characteristic relaxation time \tau , stress index n along with the apparent activation energy for creep Q_\rmappwere systematically investigated in order to probe into the deformation mechanism involved in the creep process of amorphous alloys. In parallel, a gradual transition of deformation mode from elasticity to viscoelasticity and viscoplasticity of amorphous alloys during creep was analyzed. In the framework of the quasi-point defects theory, a complete picture delineating the deformation process of amorphous creep was probed from the perspective of microstructure evolution. The results demonstrated that the creep deformation of amorphous alloy is a typical thermo-mechanical coupling and nonlinear mechanics process, which could be affected by experimental temperature, applied stress and loading time. The creep mechanism of amorphous alloy is dominated by the diffusion which is related to thermal particle flow when the applied stress is lower. On the other hand, when the stress is higher, the creep mechanism corresponds to more complicated synergistic actions consisting of both stress-induced collective rearrangements of atoms and temperature-induced thermal activation. In addition, the underlying physical background of the elastic-plastic transition of the amorphous alloy during creep deformation was described, which is correlated to the initiation of quasi-point defects as well as the formation, expansion and coalescence process of sheared micro-domains under thermo-mechanical stimuli.