Architecting a Gradient Multilayered Structure to Concurrently Strengthen and Toughen Ti/Mo Nanoscale Multilayers

Most nanoscale metallic multilayers (NMMs) exhibit ultra-high hardness but limited toughness. To toughen Ti/Mo NMMs, a gradient multilayered (GM) structure was architected via manipulating individual layer thickness (h) gradient distribution along the film growth direction. The resulting GM structure significantly raises the toughness of Ti/Mo NMMs without reducing their peak hardness. High back stress developed from the plastic incompatibilities stemmed from aggravated microstructural heterogeneity is primarily responsible for the unprecedented synergy of hardness and toughness. Our findings provide a promising approach to concurrently strengthen and toughen NMMs.