LAUSR

ABSTRACT An aluminium-containing medium manganese steel has been designed to undergo intercritical annealing followed by quenching in water and subsequent partitioning. Water quenching, replacing the quenching temperature (QT) between 150 and 300°C in conventional quenching and partitioning steels, is therefore adopted in QP alloys, in order to guarantee the precise QT in practice. The low intercritical annealing temperature of 750°C refines both ferrite and prior austenite grains into submicron size. The large fraction of ultra-fine ferrite, as well as the transformation-induced plasticity effect of retained austenite, improves the overall ductility of this water-quenched and partitioned steel. The alloy has achieved excellent mechanical properties of 1130 MPa ultimate tensile strength combined with 19.2% total elongation.