Stress-induced softening and hardening in a bulk metallic glass

To uncover the influence of pre-existing/residual stress on the mechanical behavior of metallic glass, the micro-Vickers indentation of a stressed metallic glass was studied. The pre-existing stress was introduced by bending. The results show that the nominal hardness decreases with pre-existing tensile stress and increases with pre-existing compressive stress. The real hardness decreases with pre-existing tensile stress, but does not increase obviously with pre-existing compressive stress. The mechanism of the strong hardness dependence on stress was investigated using finite element analysis. The unexpected hardness dependence on pre-existing compressive stress is also discussed.