Transformation Plasticity in Austenitic Chromium Nickel Steels That are Tough at Low Temperatures.

Four metastable Cr-Ni steels were used in experiments which revealed transformation plasticity below 0 degree C when the applied tensile stresses were lower than the yield strength. With increasing stress, the amount of plastic elongation increases and the onset of transformation plasticity is displaced to higher temperatures. With increasing austenite stability in the steels with the higher Cr plus Ni contents, these effects decreased. Steel with 20%Cr and 12%Ni showed no transformation plasticity down to minus 196C. It is pointed out that between Ms and Md the yield strength may also decrease significantly as the result of transformation plasticity. This is important when Cr-Ni steels are used in a very low temperature environment.