Quenching of High Entropy Alloys after Annealing

The effect of cooling rate after annealing at ۹۰۰ °C on the microstructure and hardness of high entropy alloys was investigated using two typical samples with the chemical composition of Co۱۶Cr۱۴.۵Fe۲۹Mn۱۱.۵Ni۲۹ and Co۱۱.۵Cr۷Fe۲۷Mn۲۷Ni۲۷(Nb۰.۰۸C۰.۵) (at%). The microstructural characterisation and hardness measurements were carried out by optical microscopy, scanning electron microscopy, wavelength-dispersive X-ray spectroscopy, electron back scattered diffraction, X-ray diffraction technique and Vickers hardness testing. A face centred cubic crystal structure matrix was observed in both alloys before and after annealing and regardless of cooling conditions. SEM analyses revealed an extensive precipitation in Co۱۱.۵Cr۷Fe۲۷Mn۲۷Ni۲۷(Nb۰.۰۸C۰.۵) alloy after annealing. It was also found that air/furnace cooling can enhance grain growth-coarsening just in Co۱۶Cr۱۴.۵Fe۲۹Mn۱۱.۵Ni۲۹. However, the hardness results generally showed insignificant hardness variations in both alloys after water-quenching, air-cooling and furnace-cooling. The results suggested that the hardness is mainly controlled by solid solution strengthening.

کلیدواژه ها:

High entropy alloys ، Cooling rate ، Annealing ، Microstructure ، Hardness