The main purpose of this investigation was to study the tensile properties of a C-Mn-Si TRIP steel compared with a dual-phase (DP) steel. Steel samples were produced by appropriate heat treatment cycles after which around 19% retained austenite and 18% martensite were formed in TRIP and DP steel samples, respectively. The volume fractions of phases in investigated steels were measured using the Clemex image analyzing software. Both the DP and TRIP steels showed characteristic tensile properties including continuous yielding, high work hardening rate and high tensile to yield strength ratio. In comparison, the overall work hardening rate of TRIP steel was relatively higher except for the beginning of tensile deformation where no sufficient amount of hard martensite phase had produced during the strain-induced austenite transformation for strengthening of the TRIP steel microstructure. Despite the TRIP steel showed higher work hardening rate and tensile strength, its uniform true strain was also higher than that of DP steel. The presence of hard martensite islands in the microstructure of DP steel was considered to be the main reason for the high work hardening rate and tensile strength of DP steel. In addition, the characteristic tensile properties of TRIP steel were attributed to the strain-induced transformation of metastable retained austenite to hard martensite phase during straining.

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