Chad W. Sinclair

On the impact of grain size distribution on the plastic behaviour of polycrystalline metals

Recent experimental studies have reported improved combinations of strength and uniform elongation in ultrafine-grained polycrystals with bi-modal grain size distributions. Despite these results, the extent to which the grain size distribution affects macroscopic tensile response, particularly at large strains, is unclear. This issue is examined here for polycrystals with varying grain sizes and grain size distributions using a grain size dependent constitutive model within the viscoplastic self-consistent formalism. The evolution of the macroscopic and grain-level stresses and strains has been monitored as a function of the width and mean of the grain size distribution. As an example of highly heterogeneous structures, the stress–strain response of a number of bi-modal microstructures have been examined and compared with their uni-modal counterparts.

Double tensile twinning in a Mg–8Al–0.5Zn alloy

The presence of deformation twinning in magnesium introduces significant challenges for predicting the bulk response of the material. In this work, we present results showing the presence of tensile twins formed within pre‐existing tensile twins in samples deformed in compression at 77 K. Such double twins mirror the observation of double compression‐tension twins previously observed. It is argued that the observed double twinning occurs due to the difficulty of non‐basal slip at the low test temperature.

Accounting for local interactions in the prediction of roping of ferritic stainless steel sheets

The effect of the spatial distribution of crystallographic orientations on roping amplitude and wavelength in ferritic stainless steel has been evaluated. The through-thicknessmechanicalbehaviourofasheetdeformedintensionhasbeen tested experimentally and simulated using a full-field viscoplastic fast Fourier transform formulation. These crystal plasticity simulations use orientation imaging microscopy data as input, allowing for large-scale simulation domains tobeinvestigatedwhileaccountingfortheclusteringoforientationswithsimilar deformation behaviour. The simulations predict both the local deformation response as well as the macroscopic surface roughness. The latter is compared quantitatively with experimental measurements and is shown to predict both the wavelength and amplitude of the observed roping. The results of these simulations have also been compared with previously proposed mean-field crystal plasticity simulations of roping, performed using the viscoplastic selfconsistent code, in which each crystal orientation is, at most, influenced by the behaviour of a homogenized matrix, but not by its local neighbourhood. Comparison between these two kinds of approaches thus allows us to assess the significance of the local neighbourhood on the macroscopic prediction of roping. (Some figures may appear in colour only in the online journal)

In-situ measurements of load partitioning in a metastable austenitic stainless steel: Neutron and magnetomechanical measurements

In order to construct physically based models of the mechanical response of metastable austenitic steels, one must know the load partitioning between the austenite and the strain-induced martensitic phases. While diffraction-based techniques have become common for such measurements, they often require access to large facilities. In this work, we have explored a simple magnetic technique capable of providing a measure of the stresses in an embedded ferromagnetic phase. This technique makes use of the coupling between the elastic strain and the magnetic response of the

A three-dimensional atomistic kinetic Monte Carlo study of dynamic solute-interface interaction

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Simulating the Topology of Recrystallization in Stabilized Ferritic Stainless Steels

-martensite in an austenitic stainless steel undergoing straining. The magnetic technique proposed here is compared to neutron diffraction measurements made on the same material and is shown to give nearly identical results. The resulting predictions of the load partitioning to the

Grain scale analysis of variant selection during the gamma-epsilon-alpha' phase transformation in austenitic steels

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