Quenching and flash-partitioning enables austenite stabilization during press-hardening processing

Quenching and flash-partitioning (Q&FP) concept is proposed based upon carbon diffusion associated with the martensitic transformation. For the Si-added steel having an elevated martensite start (M-s) temperature, carbon can diffuse rapidly from martensite laths into their adjacent austenite within only a few seconds during the martensitic transformation, to replace carbides precipitation by auto-tempering in the Si-free steel. Elevating M-s in alloy design based on the Q&FP concept enables the stabilization of retained austenite during press hardening. The transformation-induced plasticity effect of retained austenite films improved the total elongation of press-hardened steel to 10.5% combining with 1660 MPa tensile strength. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.