High-temperature mechanical behavior and microstructural destabilization evolution of the lightweight refractory high-entropy alloy prepared by laser additive manufacturing

Lightweight refractory high-entropy alloy (LRHEA) has lower density and higher specific strength, which makes it very promising for future applications in rocket engine components. Their high-temperature resistance to softening and high microstructure stability in a wide temperature range are also essential to sustaining their performance due to being used in harsh, high-temperature situations. In this work, the high-temperature tensile behavior of Al_0.3NbTi₃VZr_1.5 LRHEA fabricated by laser additive manufacturing has been systematically investigated from 400 °C to 800 °C, and the relationship between the deformed microstructure and the mechanical behavior was revealed, and analyzing the reasons for the thermodynamic instability of the solid solution in LRHEA are discussed in detail. It is found that the weakening of the high entropy effect at intermediate temperatures reduces the stability of the solid solution, and the accelerated diffusion between elements further promotes the solid solution destabilization, mainly manifested as the Laves phase and the local chemical fluctuation (LCFs). The high dislocation density introduced by the additive manufacturing technology leads to the irregular connection of the Laves phases within the grains, and it can be improved by grain growth. The high negative mixing enthalpy competes with the high-entropy effect, and temperature is the decisive factor. In this situation, the atomic clusters were promoted and induced spinodal decomposition for generating LCFs. The formation of LCFs exhibits solute competition with the emergence of the C14 Laves phase, and the phase proportions fluctuate at different temperatures. This work provides new thinking and attention for developing lightweight, heat-resistant materials.