|About this Abstract
||MS&T23: Materials Science & Technology
||Advances in Understanding of Martensite in Steels II
||Achieving 1.4 GPa Tensile Strength with Good Ductility in a Novel Low-alloy Low-carbon Martensite Steel
||Pravendra Pratap Singh, Murugesh Kumar R., Suhrit Mula, Sadhan Ghosh
|On-Site Speaker (Planned)
||Pravendra Pratap Singh
Ultra-high strength steels are designed for lightweight, cost-effective parts with improved passive-safety. Hence, a low-alloy low-carbon (0.2wt.% C) martensitic-steel has been developed by combining hot-rolling+water-quenching and tempering. The maximum yield and ultimate tensile strength are 1110MPa and 1402MPa, respectively, with 14.2% ductility for the water-quenched (WQ) sample, comparable to existing commercially used AHSS steels. The microstructural analysis indicates that the matrix contains BCC-structure martensite-laths with high-dislocation density (⁓3.5×1015 m-2). The mean average grain-size of the WQ martensite-structure is found to be 2.43μm. The dislocation (646MPa) and grain-size strengthening (282MPa) are the main contributors to yield-strength. However, with an increase in tempering temperature, the tensile-strength decreases, whereas; the impact-toughness and ductility increase. The reasons are carbon-segregation from martensite-laths to martensite grain-boundaries, dislocation-annihilation and morphology change (coarsening) in martensite-laths during tempering. Furthermore, the orientation-relationship between prior-austenite grains and lath-martensite has been studied using Kurdjumov–Sachs (K-S) orientation-relationships and correlated with strength-ductility combination.