Room temperature aging of autotempered Fe–C martensite

High-strength low-to-medium carbon martensitic steel is increasingly used in the automobile industry. This study investigated room temperature aging behavior of as-quenched autotempered Fe-C lath steels (C: 0.07-0.77 mass%) using kinetic analysis hardness change and interrupted atom probe (AP) to clarify dominating factor hardening. Age-hardening at 23 °C was confirmed steels, including low-carbon with a content less than 0.25 mass%. The AP analyses evolution indicated that growth clusters dislocations dominates hardening martensite. maximum increment martensite increased initial excess solute Csol matrix, but unit smaller carbon-supersaturated ferrite. increase may indicate concurrent softening due relaxation residual lattice strain by clustering. Interrupted prolonged over two years transformation from iron carbides occurs via an in-situ clusters. microscopic heterogeneity distribution order blocks gradual decrease during were also analysis. persistence matrix after tempering discussed.