Enhanced strength-ductility relationship in a medium Mn high Al-alloyed multicomponent steel through thermomechanical processing

A medium Mn, high Al, multicomponent steel with duplex ferrite-austenite as the starting microstructure has been designed and the influence of thermo-mechanical processing on the microstructure-texture-tensile property relationship has been investigated. The hot forging-annealing followed by hot rolling-annealing treatment showed poor combination of strength and ductility in the studied alloy. However, a subsequent cold rolling annealing or warm rolling-annealing treatment has resulted in significant improvement in strength-ductility relationship. An excellent combination of strength (1141-1184 MPa) and ductility (18.1-22.2% elongation) has been achieved in both the cold rolled-1073 K annealed and warm rolled-1073 K annealed specimens due to the presence of fine ferrite grains. Higher fraction of fine M-5(Al,Si)C precipitates have restricted the grain boundary migration thus leading to smaller ferrite grains in this annealing temperature. However, dissolution of the M-5(Al,Si)C precipitates and the simultaneous increase in the grain size of ferrite at higher annealing temperature (i.e. 1173 K and 1273 K) deteriorates the strength-ductility relationship in both the cold rolled and warm rolled specimens. The cold rolled-annealed specimens have exhibited better ductility as compared to the warm rolled-annealed specimens due to combined effect of smaller grain size as well as larger volume fraction of gamma (gamma) fiber of ferrite.