High temperature strength of refractory complex concentrated alloys

Thermodynamic and mechanical properties of 15 single-phase and 11 multi-phase refractory complex concentrated alloys (RCCAs) are reported. Using the CALPHAD approach, phase diagrams for these alloys are calculated to identify the solidus (melting, T-m) temperatures and volume fractions of secondary phases. Correlations were identified between the strength drops at 1000 degrees C and 1200 degrees C and the alloy compositions, room temperature properties, melting temperatures and volume fractions of secondary phases. The influence of alloy density on the temperature dependence of specific yield strength was also explored. The conducted analysis suggests that the loss of high-temperature strength of single-phase BCC RCCAs is related to the activation of diffusion-controlled deformation mechanisms, which occurs at T >= 0.6 T-m, so that the alloys with higher T-m retain their strength to higher temperatures. On the other hand, a rapid decrease in strength of multi-phase RCCAs with increasing temperature above 1000 degrees C is probably due to dissolution of secondary phases. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.