Effect of Cr on microstructure and mechanical properties of FeCoNiAlCrx high entropy alloys

Abstract

FeCoNiAlCrx(x=0, 0.2, 0.4, 0.6, 0.8, atomic ratio) high-entropy alloy ingots were prepared by vacuum arc melting method, and the effect of Cr content on the microstructure and mechanical properties of the alloy was investigated. The phase structure, microstructure and the composition of the alloy were analyzed and characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).The compression properties of the alloy were tested by universal testing machine. The results show that with the increase of Cr content, the microstructure of the alloy changes from a single-phase BCC structure to a BCC+FCC mixed structure; the microstructure of the alloy gradually changes from an equiaxed structure to a dendrite structure, and the grain size of the alloy is obviously refined. The five alloys prepared in this experiment have relatively good mechanical properties, and the compressive strength of the alloy increases greatly with the increase of Cr content. When x=0, the compressive strength and plastic strain of the alloy are the lowest, which are 1500 MPa and 13.56%, respectively; when x=0.8, the compressive strength and plastic strain of the alloy reach the maximum, which are 2460 MPa and 30.09%, respectively; the compressive strength of the alloy increases by 64%. It indicates that Cr addition plays an important role in the microstructure refinement, the improvement of compressive strength and ductility of FeCoNiAlCrx high-entropy alloys.

Keywords

• high entropy alloy
• phase structure
• microstructure
• mechanical property
• fractography
• compression property