Analysis of the strain-induced martensitic transformation of retained austenite in cold rolled micro-alloyed TRIP steel

Abstract

The stability of retained austenite and the kinetics of the strain-induced martensitic transformation in micro-alloyed TRIP-aided steel were obtained from interrupted tensile tests and saturation magnetization measurements. Tensile tests with single specimens and at variable temperature were carried out to determine the influence of the micro-alloying on the W temperature of the retained austenite. Although model calculations show that the addition of the micro-alloying elements influences a number of stabilizing factors, the results indicate that the stability of retained austenite in the micro-alloyed TRIP-aided steels is not significantly influenced by the micro-alloying. The kinetics of the strain-induced martensitic transformation was also not significantly influenced by addition of the micro-alloying elements. The addition of micro-alloying elements slows down the autocatalytic propagation of the strain-incluced martensite due to the increase of the yield strength of retained austenite. The lower uniform elongation of micro-alloyed TRIP-aided steel is very likely due to the presence of numerous precipitates in the microstructure and the pronounced ferrite grain size refinement.