Compositionally graded high entropy alloy with a strong front and ductile back

Abstract

Abstract Material components with graded properties can be ideal for many advanced applications due to their seamless nature of microstructural transition, cost reduction and high resistance of failure. A compositionally graded AlXCoCrFeNi (x\u2009=\u20090.3–0.7) high entropy alloy composite build was additively manufactured using laser engineered net shaping (LENS™). In this high throughput production process, the elemental composition of Al-Co-Cr-Fe-Ni powders in the hoppers were varied and the feed rates were tuned to create a laminate of Al0.3CoCrFeNi and Al0.7CoCrFeNi layers, with a 500\u2009μm wide transition zone of intermediary composition. The energy dispersive X-ray spectroscopy along the build direction verified the elemental composition matching closely with the targeted compositions. X-ray diffraction revealed the Al0.3CoCrFeNi to be a single-phase face centered cubic (fcc) structure whereas Al0.7CoCrFeNi had dual phase fcc\u2009+\u2009B2. Scanning electron microscopy was used to capture the microstructural features in the two layers as well as the transition zone. The massive shift in mechanical properties of hardness, dynamic strength and work hardening rates in this graded composite have been discussed. With this endeavor, microstructural complexity of HEAs has been combined with unique advantage of LENS™ to achieve ingenious path to fabricate materials suited applications demanding variable strength and ductility/toughness.