The effect of small stresses on the kinetics of the bainite transformation

Experiments have been conducted in which bainite is allowed to grow under the influence of an externally applied stress of magnitude less than the yield strength of austenite. By monitoring the transformation strains along two orthogonal directions, it has been possible to demonstrate that the stress in general accelerates the overall transformation kinetics, particularly at high transformation temperatures, where the chemical driving force for transformation is relatively small. An acceleration of transformation at temperatures just above the martensite start temperature has been confirmed, even in the absence of an externally applied stress. The results are interpreted in terms of the mechanism of the bainite transformation in steels.