Hierarchical crack buffering triples ductility in eutectic herringbone high-entropy alloys
High-entropy herringbone alloy
Eutectic high-entropy alloys have a dual-phase structure that could be useful for optimizing a material’s properties. Shi et al. found that directional solidification of an aluminum-iron-cobalt-nickel eutectic high-entropy alloy created a herringbone-patterned microstructure that was extremely resistant to fracture (see the Perspective by An). The structure contained lamellae of hard and soft phases, and the cracks that formed in the hard phase were arrested at the boundary of the soft phase. This, along with stress transfer, allowed a tripling of the maximal elongation while retaining high strength.
Science, abf6986, this issue p. 912; see also abk1671, p. 857
Abstract
In human-made malleable materials, microdamage such as cracking usually limits material lifetime. Some biological composites, such as bone, have hierarchical microstructures that tolerate cracks but cannot withstand high elongation. We demonstrate a directionally solidified eutectic high-entropy alloy (EHEA) that successfully reconciles crack tolerance and high elongation. The solidified alloy has a hierarchically organized herringbone structure that enables bionic-inspired hierarchical crack buffering. This effect guides stable, persistent crystallographic nucleation and growth of multiple microcracks in abundant poor-deformability microstructures. Hierarchical buffering by adjacent dynamic strain–hardened features helps the cracks to avoid catastrophic growth and percolation. Our self-buffering herringbone material yields an ultrahigh uniform tensile elongation (~50%), three times that of conventional nonbuffering EHEAs, without sacrificing strength.
