Microstructures and Properties of AlCoCrNiFe High-Entropy Alloy Sintered by Hot Oscillating Pressing Under Different Sintering Times

Powder metallurgy is an effective method for preparing high-performance powder high-entropy alloys (HEAs). Among them, the sintering time has an important effect on the microstructure, density, Vickers hardness, and corrosion resistance of AlCoCrNiFe HEAs sintered by hot oscillating pressing (HOP). Thus the effect of sintering time (0.5 h, 1 h, and 1.5 h) on the microstructure and properties of AlCoCrNiFe HEAs has been systematically investigated in this work. The results showed that the densities of HEAs alloys showed a linear relationship with the content of the FCC phase and sintering time. At the same sintering time, HOP could effectively promote the disappearance of the original particle boundary, improve the microstructure uniformity, and reduce the internal pores. The hardness and corrosion resistance properties were increased with increasing sintering time, and were better than those of the hot press (HP)-sintered samples. When the sintering time was 1.5 h, the density and hardness of a HOP-ed sample could reach 99.18% and 479.12 HV1, respectively, while the minimum corrosion current density and corrosion rate were only 6.5 mu A/cm2 and 0.055 mm/year, respectively. Thus, the hardness and corrosion resistance properties of AlCoCrNiFe had been simultaneously enhanced. Therefore, we believe that appropriately increasing the sintering time is beneficial for improving the performance of HOP-ed HEAs alloys, but this does not mean that the sintering time can be endlessly increased.