The Influence of AlFeNiCrCoTi High-Entropy Alloy on Microstructure, Mechanical Properties and Tribological Behaviors of Aluminum Matrix Composites

The microstructure, mechanical properties and tribological behaviors of aluminum matrix composites with different contents of AlFeNiCrCoTi high-entropy alloy (HEA) (4.0, 5.0 and 6.0 wt%) were investigated. The as-cast specimens were analyzed by the scanning electron microscopy and electron probe micro-analysis. The results indicated that flake-like and blocky intermetallic compounds precipitated distributing in alpha-Al matrix in the solidification when the concentration of HEA was more than 4.0 wt% in pure aluminum. Moreover, as the content of HEA increased, the number of the intermetallic compounds increased. Meanwhile, a new phase formed and it distributed inter-dendrite of alpha-Al in the solidification, which morphology was rod-shaped and the diameter was less than 200 nm. The area fraction of the nano-phases increased, and the diameter decreased with increasing the addition of HEA in pure aluminum. The tensile test illustrated that the ultimate tensile strength increased firstly and then decreased with the increase of HEA content. When the addition concentration of HEA was 4.0 wt%, the ultimate tensile strength enhanced from 58 to 142 MPa. When 5.0 wt% HEA was added into pure aluminum, the ultimate tensile strength further improved from 142 to 170 MPa. In addition, the elongation decreased from 40.6 to 22.7%. However, when 6.0 wt% HEA was added into pure aluminum, the ultimate tensile strength and elongation reduced to 157 MPa and 18.2%, respectively. The tribological behaviors of aluminum matrix composites were investigated under the condition of seawater. The friction coefficient and wear rate of aluminum matrix composites significantly decreased with the increase of HEA content. Moreover, when the addition level was up to 6.0 wt%, the friction coefficient of aluminum matrix composites decreased by 71.1% from 0.83 to 0.24, and wear rate decreased by 90.8% from 2.48 x 10(-9) m(3) N-1 m(-1) to 2.27 x 10(-10) m(3) N-1 m(-1).

Automated summary

The study showed that increasing the content of AlFeNiCrCoTi high-entropy alloy in aluminum matrix composites lead to improved mechanical properties and tribological behaviors at first, but decreasing trends were observed after a certain addition level.