| Abstract Scope |
Two copper-modified steels were analysed for phase composition and mechanical properties after quenching and tempering (Q&T). Precipitates were characterized using high-resolution transmission electron microscopy (HR-TEM), and their mean radius, number density, and volume fraction were estimated via MatCalc simulation. In HCu steel, cooperative and short-range diffusion primarily led to the formation of degenerate pearlite, while LCu steel exhibited reduced pearlite formation. The mechanisms of softening and hardening during tempering were explored, focusing on the transition of Cu precipitates from coherent BCC to incoherent FCC through semi-coherent 9R crystal structures. HCu samples demonstrated higher yield strength (YS) and ultimate tensile strength (UTS). After 0.75 hours of tempering, LCu steel achieved a strength of 811 MPa, ductility of 19.35%, hardness of 267±4 HV, and tensile toughness of 146×105 kJ/m³. The study established a detailed correlation between microstructure and mechanical properties through fractographic analysis and the coherency of various precipitates. |