Creep deformation and stress-induced structural disorder near T-g in a Zr55Al10Ni5Cu30 glassy alloy

Creep deformation under a constant applied load in a Zr55Al10Ni5Cu30 glassy alloy at the glass transition region is investigated. At an initial stress, sigma (0), less than a critical stress, sigma (c)=80 MPa, the glass shows a Newtonian flow. When sigma (0)greater than or equal to sigma (c), the flow viscosity, eta, initially decreases and attains a minimum. It then increases as the true stress, sigma, decreases with further deformation. The initial decrease in eta and the attendance of viscosity minimum are due to the stress-induced structural disorder and the structural equilibration with the applied stress, respectively. For stress, sigma, less than the viscosity minimum stress, the stress dependence of viscosity, eta(sigma), curves all tend to merge together, and is fitted well with a master curve, eta(sigma), established previously for the steady-state flow under constant strain-rate experiments. These results render further support to the hypothesis of stress-induced structural disorder and the concept of fictive stress. (C) 2001 American Institute of Physics.