Evaluation of microstructure and mechanical property variations in AlxCoCrFeNi high entropy alloys produced by a high-throughput laser deposition method

TL;DR

This study rapidly produced and analyzed 21 AlxCoCrFeNi high entropy alloys via laser alloying, revealing how Al content influences crystal structure and mechanical properties, and demonstrating the method's effectiveness for alloy design.

Contribution

It introduces a high-throughput laser alloying approach for systematically studying microstructure and properties in high entropy alloys.

Findings

Crystal structure transitions from FCC to BCC/B2 with increasing Al.

FCC phase is mainly at grain boundaries at high Al content.

Mechanical properties of laser-processed alloys align with cast alloy data.

Abstract

Twenty-one distinct AlxCoCrFeNi alloys were rapidly prepared by laser alloying an equiatomic CoCrFeNi substrate with Al powder to create an alloy library ranging x=0.15-1.32. Variations in crystal structure, microstructure and mechanical properties were investigated using X-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy and nanoindentation. With increasing Al content, the crystal structure transitioned from a disordered FCC to a mixture of disordered BCC and ordered B2 structures. While the onset of BCC/B2 formation was consistent with previously reported cast alloys, the FCC structure was observed at larger Al contents in the laser processed materials, resulting in a wider two phase regime. The FCC phase was primarily confined to the BCC/B2 grain boundaries at these high Al contents. The nanoindentation modulus and hardness of the FCC phase increased with Al content, while the properties of the BCC/B2 structure were insensitive to composition. The structure and mechanical properties of the laser-processed alloys were surprisingly consistent with reported results for cast alloys, demonstrating the feasibility of applying this high-throughput methodology to multicomponent alloy design.