Critical Strengths for Slip Events in Nanocrystalline Metals: Predictions of Quantized Crystal Plasticity Simulations

摘要

This article studies how the mono tonic and syclic stress-strain response of nanocrystalline (NC) metals is affected by the grain-to-grain distribution of critical strengths (τ_c) for slip events, as well as plastic predeformation (ε_(pre)~p). This is accomplished via finite element simulations that capture large jumps in plastic strain from dislocation slip events-a process referred to as quantized crystal plasticity (QCP).[1] The QCP simulations show that %c and ε_(pre)~p significantly alter the monotonic and cyclic response at small strain, but only τ_c affects the response at large strain. These features are exploited to systematically infer the τ_c and ε_(pre)~p characteristics that best fit experimental data for electrodeposited (ED) NC Ni. Key outcomes are the following:(1) the τ_c distribution is truncated, with an abrupt onset of slip events at a critical stress;(2) ε_(pre)~p = -0.4 pct, signifying precompression; (3) there is reverse slip bias, meaning that reverse slip events are easier than forward events; and (4) highly inhomogeneous residual stress states can be enhanced or reduced by tensile deformation, depending on ε_(pre)~p.