High-entropy alloy reinforcement in aerospace-grade aluminum 7075: A study of yield strength and elastic modulus

Abstract

This research aims to identify an appropriate theoretical model for assessing the yield strength and elastic modulus of a composite material consisting of aerospace-grade aluminum 7075 base matrix reinforced with nanocrystalline high-entropy alloy particle (HEAp) composed of CrCuFeMnNi. To fabricate the aluminum composite with a high-entropy alloy base, an innovative casting method was utilized. This method involved the use of a modified bottom-pouring stir casting furnace, integrated with a mechanical supersonic vibrator and a squeeze infiltration setup. The measured theoretical density was higher than the actual density, while the cast specimen exhibited porosity below 6.6%. Scanning electron microscopy (SEM) images revealed the presence of strengthening precipitates and a uniform dispersion of HEAp in the composite. Comparing the developed HEAp composites (CH2, CH3, and CH4) with the base AA7075 cast CH1 (AA7075 + 0 wt.% CrCuFeMnNi-HEAp), the ultimate tensile strength increased by 4% for CH2 (5 wt.% CrCuFeMnNi-HEAp), 21% for CH3 (10 wt.% CrCuFeMnNi-HEAp), and decreased by 9% for CH4 (15 wt.% CrCuFeMnNi-HEAp). Similarly, the yield strength increased by 10% for CH2, 24% for CH3, and decreased by 5% for CH4. The elongation showed an increasing trend of 5% for CH2, 12% for CH3, and 2% for CH4. The flexural strength of the HEAp composites (CH2, CH3, and CH4) increased by 2%, 5%, and 10%, respectively. The proposed model yielded similar yield strength values that closely aligned and were consistent with the experimental value within a deviation of 3.32%. The modified Halpin-Tsai models agreed with experimental value up to a reinforcement volume fraction of 4.89% when calculating the elastic modulus. The proposed model and the Hashin-Shtrikman upper bound also agreed on values up to a 3.32% reinforcement volume fraction.