抄録
Static flow stress decreases abruptly when ultrasonic oscillatory stress (17.8 kHz) is intermittently superposed. The decrement in static flow stress, Δσ, was measured in an Al–5 at%Mg alloy. Ranges of strain rate and testing temperature were from 1×10−4 to 1×10−3 s−1 and from 473 to 673 K, respectively. Δσ at 673 K was zero irrespective of superposed oscillatory stress amplitudes. This implies that the dislocation velocity at 673 K is proportional to the effective stress. Δσ’s at 473 and 573 K were dependent on oscillatory stress amplitudes, strain rates and testing temperatures. These experimental results indicate that the dislocation velocity-effective stress exponent, m∗, is greater than unity at lower temperatures. The change in m∗ with temperature and strain rate is satisfactorily explained in terms of a solute-dislocation interaction.
