Thermal physical properties of high entropy alloy Al0.3CoCrFeNi at elevated temperatures

In high entropy alloys (HEAs), the nanoscale precipitations and short-range orders affected the material's mechanical properties and brought about changes in the thermal physical properties. As-cast Al0.3CoCrFeNi was prepared, and an ideal random disorder HEA model was established by molecular dynamics (MD). The resistivity, thermal conductivity, specific heat capacity and linear expansion coefficient at 300-1100 K were obtained and discussed by experiments and simulations. The intracrystalline segregation was observed in the as-cast HEA. At about 600-800 K, the resistivity growth stagnated, and two exothermic and one downward heat capacity peaks were found in DSC and specific heat, respectively. The metastable structure of as-cast HEA was ordered and a small amount of nano-phase precipitated. When above 800 K, the resistivity increased rapidly, DSC and specific heat appeared endothermic peak and extensive range upward heat capacity peak respectively. The alloy underwent an order-disorder transition accompanied by a small amount of phase decomposition. Phonons were the main force of heat conduction. Thermal conductivity and lattice thermal conductivity show the weak temperature dependence of T-0.66 and T-0.48, respectively. The experimental results, affected by intragranular segregation and ordering, differed from the simulation results at lower temperatures while agreed well with the simulation results at higher temperatures. The order degree on thermodynamic parameters of as-cast HEA during the heating process should be considered in subsequent studies. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

In high entropy alloys, the nanoscale precipitations and short-range orders greatly impact the material's mechanical properties and thermal physical properties. Experimental and simulation results showed that the intragranular segregation and ordering in the as-cast high entropy alloy have significant effects on its resistivity, thermal conductivity, and specific heat capacity. The alloy undergoes an order-disorder transition and phase decomposition during the heating process. Phonons play a dominant role in heat conduction. The temperature dependence of thermal conductivity and lattice thermal conductivity is observed. The experimental results are affected by intragranular segregation and ordering, showing differences with the simulation results at lower temperatures but good agreement at higher temperatures.