Influence of nanoparticles on the compressive rate-sensitivity of magnesium alloys

Abstract

A numerical model to describe the onset of tension twining in magnesium alloys, which incorporates the influence of nanoparticles and strain rate, is proposed. This model is employed in conjunction with crystal plasticity, to study the compressive flow stress of magnesium alloys at strain rates from 10−3/s to 103/s. The results show negative strain rate sensitivity (SRS) for the flow stress during the initial phase of plastic deformation, which is consistent with experimental results. The influence of nanoparticles on restraining twinning is demonstrated to diminish with strain rate, and regarded as the underlying mechanism for the negative SRS. The combined effects of nanoparticle presence, strain rate, grain size and initial texture on the compressive flow stress of nanoparticle-reinforced magnesium alloys, are investigated using the proposed model. Grain size and texture are shown to affect the SRS significantly, and a critical grain size (i.e., ∼2 µm) is identified from the simulations. When grains are smaller than this critical value, a negative SRS is observed. When the initial texture is changed, the numerical results show a transition from a negative SRS to a positive one.