Effect of Heat Treatment on the Microstructure, Phase Distribution, and Mechanical Properties of AlCoCuFeMnNi High Entropy Alloy

The present paper reports the synthesis of AlCoCuFeMnNi high entropy alloy (HEA) with arc melting process. The as-cast alloy was heat treated at 900 degrees C for 8 hours to investigate the effect of heat treatment on the structure and properties. Microstructural and mechanical properties of the alloy were analyzed together with the detailed phase analysis of the samples. The initially as-cast sample was composed of two separate phases with BCC and FCC structures having lattice parameters of 2.901 angstrom and 3.651 angstrom, respectively. The heat-treated alloy displays microsized rod-shaped precipitates both in the matrix and within the second phase. Rietveld refinement has shown that the structure was having three phases with lattice parameters of 2.901 angstrom (BCC), 3.605 angstrom (FCC1), and 3.667 angstrom (FCC2). The resulting phases and distribution of phases were also confirmed with the TEM methods. The alloys were characterized mechanically with the compression and hardness tests. The yield strength, compressive strength, and Vickers hardness of the as-cast alloy are 1317 +/- 34MPa, 1833 +/- 45MPa, and 448 +/- 25Hv, respectively. Heat treatment decreases the hardness values to 419 +/- 26Hv. The maximum compressive stress of the alloy increased to 2123 + 41MPa while yield strength decreased to 1095 +/- 45 with the treatment.