High Ductile Medium Mn Lightweight Alloy: The Role of Intensive Quenching and Deep Cryogenic Treatment

Medium Mn lightweight steels with a relatively higher content of 9–12 wt% have been actively developed recently to meet the demands crashworthiness and vehicles. In this study, combined intensive quenching (IQ) deep cryogenic treatment (DCT) was first proposed achieve microstructural homogeneity as well final strength–ductility synergy medium segregation bands, together comparison conventional intercritical annealing. The IQ DCT process induced formation finer large fractioned plate-like martensite in austenite matrix thereby contributed uniform grains after subsequent martensitic transformation rate (dVγ/dε) kinetics (k value) were used evaluate mechanical stability retained austenite, showing that D700&750 sample exhibited similar dVγ/dε value extremely low k when compared IA650–850 samples, implying former had austenite. enabled TRIP effect occur larger strain range, leading continuous hardening behavior. Thus, highest yield strength (728 MPa) largest total elongation 61.6% achieved sample, where ductility more than three times IA samples. grain size morphologies believed be main factors influencing strain-hardening behavior type ultrafine lamellar equiaxed ferrite duplex structure.