STRESS AFFECTED BAINITIC TRANSFORMATION IN A FE-C-SI-MN ALLOY

Isothermal transformation experiments are reported in which the format ion of bainitic ferrite occurs under the influence of stresses below t he yield strength of the austenite. The response of the transformation was monitored by simultaneously measuring the longitudinal and radial transformation strains. This enabled the dilatational and deviatoric strain components to be deconvoluted from the total transformation str ain. The data have been analysed by comparison with a theoretical mode l for the stress-assisted growth of bainite. The results confirm that the microstructure readily responds to stresses well below the yield s trength of the parent phase. Furthermore, those crystallographic varia nts which are favoured by the stress grow first in the sequence of tra nsformation. Experiments where the stress just exceeds the yield stren gth are also reported.