Deformation behavior of a commercial Ni-20%Cr alloy

Deformation behavior of a commercial Ni-20%Cr alloy containing dispersoids was studied in the temperature range from 600degreesC to 950degreesC over five orders of magnitude of strain rate. It is shown that the Ni-20%Cr alloy exhibits a threshold behavior, like that in superalloys produced via mechanical alloying technique. It was demonstrated, by incorporating a threshold stress into the analysis, that the alloy exhibited three characteristic modes of deformation behavior. At the normalized strain rate, epsilonkT/(D(1)Gb) less than ranging 10 the value of the true stress exponent, n, is similar to4. The true activation energy for plastic deformation, Q(c), in this range is 285 30 kJ/mol. In the normalized strain rate range 10(-8) - 10(-4), the value of the true stress exponent, n, is similar to6, and Q(c) value tends to decrease to a value of 175+/-30 kJ/mol. This change in deformation behavior with decreasing temperature was interpreted in terms of transition from high temperature climb, controlled by lattice diffusion, to low temperature climb, controlled by pipe-diffusion. At epsilonkT/(D(1)Gb)=10(-4) the power-law breakdown is observed and at higher normalized strain rates there is a range of exponential creep. A temperature dependence of normalized threshold stress was found in the temperature range 750-950degreesC. Value of the energy term, Q(c), was found to be about 18.5 kJ/mol and tends to increase at lower temperature range.