Effect of Al Content on Microstructure, Mechanical, and Corrosion Properties of (Fe33Cr36Ni15Co15Ti1)100-xAlx High-Entropy Alloys

(Fe33Cr36Ni15Co15Ti1)(100-x)Al-x (x = 0, 3, 5, 6, 7, 8) high-entropy alloys (HEAs) are prepared by arc melting. The influence of Al element addition on the microstructure, mechanical properties, and anticorrosion in 3.5 wt% NaCl aqueous solution is systematically investigated. The microstructure analysis indicates that HEAs possess varying phases from face center cubic/face-centered cubic (FCC) + sigma to FCC + body-centered cubic (BCC) and then FCC + BCC + sigma, the last to BCC + sigma with the increase of Al content. The compressive results suggest that the Al addition exhibits a significant elevation in strength. Particularly, Al7 alloy shows a superior strength and plasticity, which presents a yield strength of 1315.3 MPa and a compressive strain over 50%. Order strengthening and coherent strengthening of nanosized phase are regarded as main strengthening effects. In addition, Al element is harmful for the corrosion resistance of (Fe33Cr36Ni15Co15Ti1)(100-x)Al-x HEAs system, which is ascribed to the weakened passive film stability. It is also noted that pits tend to be initiated in relatively Cr-depleted phases (FCC or B2 phase) due to the inhomogeneous elemental distribution-induced galvanic corrosion. In spite of this, all HEAs exhibit superior corrosion resistance than that of 304SS.

Automated summary

This study investigates the influence of Al element addition on the microstructure, mechanical properties, and corrosion resistance of high-entropy alloys (HEAs). The results show that the addition of Al significantly improves the strength and plasticity of the alloys but is harmful to their corrosion resistance. Nevertheless, all HEAs exhibit superior corrosion resistance compared to 304 stainless steel.