Microstructural evolution during deformation of heterostructured dual-alloy composites

Abstract

Two heterostructured metal composites (HMCs) have been fabricated by hot isostatic pressing (HIPing); i) a mixture of two steel powders (SA508 and 316L) and ii) a mixture of two titanium powders (Ti-6Al-4V and Beta C). They are heterogeneous in terms of grain size, morphology and phase distribution. In the as-HIPed conditions, the steel HMC comprises a soft austenitic matrix with harder martensitic islands while for the Ti HMC, the domains have similar strength. For both systems, the HMCs show significant improvements in strength with little detriment to ductility relative to the monolithic alloys. In both cases, loading-unloading-reloading tensile tests confirm the generation of significant hetero-deformation-induced (HDI) stresses with straining. Macroscopic optical digital image correlation (DIC), EBSD and high-resolution DIC analyses, all acquired in situ during loading, reveal significant strain partitioning between the domains at low strains. For the titanium HMC, the interphase region controls strain partitioning and transfer between Ti-6Al-4V and Beta C domains. More widely, there is the potential to make many heterostructured metals composites by HIPing mixed alloy powders.