Optimization of Q&P steels

Quench and Partioning (Q&P) steels are 3rd generation advanced high strengths (AHS) steels. They consist of a martensite-austenite microstructure created during a quenching process. However, due to the subsequent partitioning treatment the martensite is relatively soft and the austenite relatively stable against phase transformation which makes the alloy strong (tensile strength up to 1000 MPa) and ductile (uniform tensile elongation up to 20 %) at the same time. We aim at improving the microstructure by obtaining finer austenite dispersion.

Left: Microstructure of a typical Q&P steel, as measured by EBSD-based ORM. Coloured grains correspond to austenite, bright gray is primary martensite (partitioned), dark gray secondary martensite (non-partitioned).
Right: Schematics of the thermal treatment of a Q&P steel. Primary martensite is formed during the first quenching, secondary martensite during the second.
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