Microstructure and tensile behaviour of cold-rolled TRIP-aided steels

The transformation of austenite to martensite is fundamental to the hardening of carbon steels. This transformation plays an important role for the mechanical behaviour of low-carbon ferrous alloys containing about 10 vol.% retained austenite. The effect, known as transformation-induced plasticity (TRIP), is manifested by unusual high work hardening and high uniform elongation - properties very desirable for thin sheets applied for automotive parts. Tensile tests of cold-rolled sheets at room temperature allowed to study the retained austenite stability against strain-induced martensitic transformation. The influence of the processing texture (specimen orientation) and the strain rate (2 × 10^-2 and 2 × 10^-3 s^-1) on the uniform elongation was observed experimentally. Results show that a homogeneous microstructure and the absence of initial blocky martensite ensure long deformation paths. At the same time, tensile data reveal only a small influence of deformation parameters on the ultimate strength.