The spall and anomalous inelastic response of Galfenol to shock loading

Abstract

Plate impact experiments were performed to probe the dynamic response of Galfenol, specifically the Hugoniot elastic limit (HEL), spall strength, and failure characteristics. Galfenol exhibits low HEL and high spall strength as compared to α-Fe, possibly owing to the large grain size and strong texture. A cusp is observed on the velocity–time profiles that exhibits pronounced stress and strain rate dependence. The nature of this cusp is not well understood, but it may possibly be related to the ferromagnetic-to-paramagnetic second order phase transformation induced by shock waves. Shock-recovered specimens exhibit brittle intergranular fracture under compressive loading with cracks initiating and growing along the shock direction. It is expected, though not confirmed, that these cracks grow along grain boundaries owing to embrittlement by Ga segregation at the boundaries.