Effect of Heat Treatment Temperature on the Microstructure and Mechanical Properties of Cu 0.3 Cr 2 Fe 2 Ni 3 Mn 2 Nb x High-Entropy Alloys.

The effects of heat treatment temperature on the microstructure and mechanical properties of Cu_0.3Cr₂Fe₂Ni₃Mn₂Nb_x high-entropy alloys (HEAs) were studied. Results indicate that in the as-cast state, an Nb₀ alloy is composed of a single FCC phase, and a Laves phase gradually forms as Nb content increases. After heat treatment at 800 °C, BCC solid solution phases rich in Cr, Fe, and Mn form in all alloys. The BCC phases in the Nb_0.2 and Nb_0.4 alloys decompose after heat treatment at 900 and 1000 °C, respectively, and the microhardness of the as-cast Cu_0.3Cr₂Fe₂Ni₃Mn₂Nb_x HEAs increases from 127 to 203 HV with increasing Nb content. After heat treatment, the microhardness of the alloys considerably improves, and the Nb_0.4 alloy has the highest microhardness after heat treatment at 800 °C (approximately 346 HV). After heat treatment at 900 and 1000 °C, the microhardness of the three alloys decreases. The yield strength of the as-cast Cu_0.3Cr₂Fe₂Ni₃Mn₂Nb_x HEAs increases with Nb content and shows a trend of first increasing and then decreasing with increasing heat treatment temperature. The strengthening mechanism of the heat-treated alloys is mainly attributed to the second-phase strengthening of the Laves phase and the solid solution strengthening of the BCC phase. [ABSTRACT FROM AUTHOR]