Revisiting Strengthening Mechanisms in Ultrahigh Strength Martensitic Steel: Role of Solute Carbon and Precipitation Behavior

This study presents a quantitative analysis of the strengthening mechanisms influencing the yield strength of low‐carbon, ultrahigh‐strength martensitic steels subjected to quenching and tempering. Four principal mechanisms—solid solution strengthening, grain boundary strengthening, dislocation strengthening, and precipitation strengthening—are systematically evaluated using advanced microstructural characterization techniques. The results showed that grain boundary strengthening is relatively insensitive to tempering temperature, while dislocation and solid solution strengthening are notably enhanced at lower tempering temperatures due to sluggish recovery and the retention of solute carbon, respectively. Although precipitation strengthening did not make a significant contribution, it strongly influences solid solution strengthening by modulating the solute carbon concentration. Accounting for the effect of solute carbon substantially improves the correlation between calculated and experimental yield strengths. This study highlights the interplay between precipitation hardening and solid solution strengthening in determining the mechanical properties of martensitic steels, providing valuable guidance for alloy design and heat treatment optimization.