Gradient Structure Produces Superior Dynamic Shear Properties

Abstract

This chapter reports that gradient-structured metals have much superior dynamic shear properties over homogeneous nanostructured (NS) metals. The gradient structure was found to delay the nucleation of adiabatic shear bands (ASB) at the NS surface layers and to reduce the propagation speed of ASB by an order of magnitude as compared with homogeneous materials. Metals and alloys with both high strength and ductility have been pursued by scientists and engineers for several decades. Hetero-deformation induced hardening has been reported to play a significant role in the mechanical behavior and properties of gradient structures, similar to what occurs in other heterostructures. The gradient structure delayed the initiation of ASB on the nanostructured surface and dramatically slowed down the ASB propagation by an order of magnitude rendering the gradient materials higher dynamic shear toughness. The superior dynamic properties of the gradient materials are derived from its strain gradient during dynamic shear deformation, which produces a geometrically necessary dislocations and strong HDI hardening.