High Temperature {111} Slip Behavior of a Directionally Solidified Ni3Al Alloy

The deformation behavior of {111} slip in a directionally solidified (DS) Ni 3 Al-Zr-B alloy has been investigated in tension in the temperature range of 773-1373K. At 0.2% strain, deformation rate was found to be exponential with yield stress above the peak temperature (1023K). However, at a larger strain of 3.8% strain, deformation rate on flow stress obeyed a power law relation above the peak temperature, with the stress exponent n=4.89 in the temperature range of 1073-1173K, suggesting a deformation mechanism of edge dislocation climb, and n=2.70 in the temperature range of 1273-1373K, suggesting a deformation mechanism of viscous screw dislocation glide. The dislocation structure developed with increasing stress and strain, the dislocation density, ρ, was related to the applied stress, σ, as ρσ 1.7 , and no steady state dislocation density was achieved up to 3.8% strain. With increasing temperature, the activation volume decreased below the peak temperature, and stayed constant at a low level above the peak temperature, reflecting two different processes of thermal activation or unpinning of the Kear-Wilsdorf locks.