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The Quenching and Partitioning (Q&P) process is known as a promising method for producing steels with superior mechanical properties. Developing Q&P steels with optimized mechanical properties requires well understanding of the relation between their microstructural and mechanical properties. The microstructural evolution during different Q&P processes in a 0.3C-1.5Si-3.5Mn (wt.%) steel was analysed. Mechanical properties of the developed microstructures were measured by using microtensile test. The influence of volume fractions and carbon contents of the phases on the ductility and strength of the microstructures was investigated. Furthermore, the effect of the specimen size on the tensile properties was discussed and a correction procedure was applied to convert the measured microtensile properties to the standard ones. A comparison with the measured mechanical properties of other type of Advanced High Strength Steels (AHSS) shows the improved properties of the Q&P steels.

The Quenching and Partitioning (Q&P) process is a promising method for developing steels with superior mechanical properties. This process includes quenching an austenitic microstructure to form a controlled fraction of martensite, an isothermal treatment (partitioning step) aiming for the partitioning of carbon from martensite to austenite and a final quench to room temperature. This paper analyses the concurrent processes of carbon partitioning and martensite tempering during the partitioning step of a 0.3C-1.5Si-3.5Mn (wt.%) Q&P steel. The influence of the martensite tempering and the carbon partitioning on the tensile strength as well as on the uniform and post-uniform elongation of the developed Q&P microstructures is investigated.