Precipitation enhancing strain hardening capability of ductile AlTiVZrNb high-entropy alloys upon dynamic loading

Abstract

Strain softening upon dynamic loading is a roadblock of most body-centered cubic (BCC) structured high entropy alloys (HEAs), which can easily lead to dynamic plastic instability. Here, the precipitation was applied in Al–Ti–V–Zr–Nb system BCC HEAs for enhancing strain hardening capability upon dynamic loading. The α2 precipitates (D019 structure, P63/mmc space group) with contents of ∼25% are developed with burgers orientation relationship (BOR) interface and homogenously dispersed in the BCC matrix. The α2 precipitates can effectively reduce the slip length, activate more slip systems, and impose high density geometrically necessary dislocations near interface for hardening. Owing to the BOR, dislocations can slip transfer across phase boundaries offering the co-deformation for plasticity. Compared with single BCC counterpart, the strain hardening rate is changed from negative to positive and the fracture feature transforms from cleavage to dimples. Consequently, a ∼60% increasement in the product of strength and ductility is achieved upon dynamic loading.