Directional solidification of the Al0.8CrFeNi2.2 eutectic high-entropy alloy

Abstract

The concepts of high-entropy alloys and eutectic in-situ composites have been applied as an interesting approach to achieve materials with an improved balance between strength and ductility. In this study, the Al0.8CrFeNi2.2 eutectic high-entropy alloy (EHEA), formed by the ordered body-centered cubic (B2) NiAl-rich and face-centered cubic (FCC) CrFeNi-rich phases, was fabricated through arc melting and directionally solidified in a Bridgman setup at translation rates of 1.4–14 μm/s. At the lowest rates, growth occurred with a planar solid–liquid interface, resulting in a highly regular lamellar array. As the translation rate increased, an interface transition from planar to cellular occurred, resulting in eutectic grains surrounded by layers of anomalous eutectic structure. The dependence of the lamellar spacing on the growth rate was established, along with the relationship between them and the Vickers hardness. Finally, the mechanical behavior was assessed by tensile tests, revealing that the translation rate increases the yield strength without sacrificing ductility. The directionally solidified Al0.8CrFeNi2.2 EHEA exhibited a maximum yield strength of approximately 558 MPa with reasonable ductility (total elongation of approximately 6.5 %) under the analyzed conditions.