Effect of Al Content on Microstructure, Mechanical and Corrosion Properties of (Fe33cr36ni15co15ti1)100− X Al X High Entropy Alloys

(Fe33Cr36Ni15Co15Ti1)100− x Al x (x=0, 3, 5, 6, 7, 8) high entropy alloys (HEAs) were prepared by arc-melting. The influence of Al element addition on the microstructure, mechanical properties, and anti-corrosion in 3.5 wt.% NaCl aqueous solution was systematically investigated. The microstructure analysis indicated that HEAs possessed varying phases from FCC+Sigma to FCC+BCC and then FCC+BCC+Sigma, the last to BCC+Sigma with the increase of Al content. The compressive results suggested that the Al addition exhibited a significant elevation in strength. Particularly, Al7 alloy performed a superior strength and plasticity, which presented a yield strength of 1315.3 MPa and a compressive strain over 50%. Order strengthening and coherent strengthening of nanosized phase were regarded as main strengthening effects. In addition, Al element was harmful for the corrosion resistance (Epit and Icorr) of (Fe33Cr36Ni15Co15Ti1)100− x Al x HEAs system, which was ascribed to the weakened passive film stability. It was also noted that pits tended 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. This work provides a beneficial guidance for alloy design simultaneously regarding strength, ductility, and corrosion.