Mechanism of Internal Stress Superplasticity Based on Thermally- Activated Kinetics

摘要

Three main theoretical models for internal stress superplasticity (Greenwood and Johnson, Sherby et al., and Sato and Kuribayashi) were reexamined with respect to the temperature profile of the thermal cycling. Assuming a mismatch strain rate obeying a power-law, we concluded that three constitutive equations were essentially identical except for constant terms. It is predicted that the apparent activation energy of internal stress superplasticity is equal to 1/n (n: stress exponent of isothermal power-law creep) times that of isothermal power-law creep. This theoretical prediction has been experimentally verified by the thermal cycling creep tests using the same temperature profiles with several equivalent temperatures in Al-Be eutectic composite.