| Abstract Scope |
This study explores the synergistic effects of co-precipitating Mn, Ni, and Cu in quenched and tempered steels. Homogenized and forged steel blocks underwent Q&T treatment at 920℃ (quenching) and 650℃ (tempering). Microstructural analysis using SEM, TEM, and simulations via MatCalc and Thermo-Calc revealed Cu-rich precipitates, which significantly enhance hardness and toughness. CCT curves simulated with JMatPro indicated improved hardenability with increasing Cu content, leading to a higher volume fraction of degenerate pearlite. After 45 minutes of tempering, the steel demonstrated high strength (811 MPa), ductility (19.35%), hardness (267±4 HV), and tensile toughness (146×10⁵ kJ/m³). The enhanced toughness is attributed to grain refinement from complex carbides and nano-sized, shearable Cu precipitates. The study further examines the impact of varying Cu content on mechanical properties, including the transformation of Cu precipitates from BCC (coherent) → 9R (semi-coherent) → FCC (incoherent) structures. Fractography and misfit analysis link these microstructural changes to mechanical behavior. |