Design of tough, ductile direct quenched and partitioned advanced high-strength steel with tailored silicon content

The novel processing concept of direct quenching and partitioning (DQ&P) has been explored with a medium-carbon (0.4 wt.% C) steel to evaluate optimize the route for excellent property combinations. New compositional design approach was based on physical simulation studies aiming understand influence varying silicon contents (1.5, 0.75 0.25 wt.%) Q&P parameters microstructural development including carbide formation retained austenite stabilization. Optimized were selected DQ&P laboratory hot-rolling trials analyses data. overall aim study produce ultrahigh-strength structural steels yield strength ?1100 MPa combined high uniform total elongation impact toughness, achieved through designing low-temperature effective carbon partitioning. gained an combination mechanical properties comprising ?1000–1200 tensile ?2100–2300 MPa, good (?11–13%), moderate toughness transition temperature T 28J ? (?5 +12 °C). Straining prior led extensive refinement final martensitic-austenitic nanostructure. Formation nanoscale lath-martensite fine film-like structures enabled observed improvement properties. Besides nano-twinned martensite, inter-lath transitional carbides comprehensively characterized. No adverse effect prolonged during slow cooling, simulating coiling in actual industrial practice, noticed suggesting new possibilities developing tough, ductile both strip/plate products.