Hardness and strength values of over 55 copper alloys strengthened by solid solution strengthening, precipitation hardening, cold working, and dispersion strengthening were compiled. The yield strength (YS) and ultimate tensile strength (UTS) values of the copper alloys examined ranged between 50 to 1300 MPa and 200 to 1400 MPa, respectively. The compiled values were classified based on strain-hardening potential an indirect method to understand the effect of strain-hardening characteristics. Least squares regression analysis was employed to establish correlations between strength and Vickers hardness values. Strain-hardening potential showed a significant effect on the correlations. In all the cases, a linear relation was obtained for both YS and UTS with hardness for the entire range of values under analysis. Simple empirical equations were proposed to estimate the strength using bulk hardness. The proposed correlations obtained for the entire range of values were verified with experimental values. A good agreement was observed between experimental and predicted values.

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In the present investigation, 15Cr‐5Ni‐1Mo‐1W martensitic stainless steel was studied for the microstructure and mechanical properties after heat treatment (solution treatment, cryo treatment, and aging). A combination of high strength and ductility was obtained by cryo treatment (−70°C for 2 h), and aging (500°C for 2 h). Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were employed to identify the phases in the steel. TEM studies have shown the presence of retained austenite and large (Nb,V)C carbides in the martensite matrix after solution treatment. Aging at 500°C for 2 h has shown precipitation of fine Mo2C precipitates in the martensite matrix. The increase in strength after cryo treatment and aging is attributed to transformation of retained austenite and precipitation of fine Mo2C precipitates, respectively. The yield strength of the steel in aged condition calculated based on the Orowan strengthening is in good agreement with the experimental value considering the softening induced by reversed austenite. The present steel showed yield strength and ultimate tensile strength of 1050 and 1235 MPa, respectively with a ductility of 20.4%. This paper brings out the details of the investigation results and a correlation between microstructure and strength.

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