Correlations to improve room temperature ductility of refractory complex concentrated alloys

Room temperature tensile and compressive properties of refractory complex, concentrated alloys (RCCAs) have been analyzed to explore correlations capable of anticipating ductility in this growing class of structural materials. The Pugh-Pettifor and Rice-Thomson ductility criteria are generally satisfied by the current dataset, but the dataset does not cover a sufficiently wide range to provide a critical evaluation. A previously suggested ductility criterion based on the average valence electron concentration (VEC) of an alloy, i.e. abrupt ductile to brittle transition at VEC = 4.5, is not supported in the present study. A revised VEC criterion is suggested, but the data supporting this trend is sparse and additional work is needed. These three ductility criteria are evaluated using only single-phase RCCA data. A new ductility criterion based on the RCCA yield strength (sigma y) is suggested from the present work, using both single-phase and multi-phase data. RCCAs with commercially relevant tensile ductility have sigma y < 1200 MPa, and alloys with compressive ductility of >30% (analyzed here to provide useful tensile ductility) have sigma y < 1500 MPa. Strengthening models to predict sigma y in RCCAs may thus be used to anticipate alloys that may also possess useable levels of ductility.

Automated summary

The study analyzed the room temperature tensile and compressive properties of refractory complex, concentrated alloys (RCCAs) to explore correlations capable of anticipating ductility in this class of structural materials. A new ductility criterion based on the RCCA yield strength was suggested, but more data and research are needed to support this trend. Predictive models for estimating the yield strength in RCCAs could help identify alloys with usable levels of ductility.