Publications

A shear transformation zone dynamics numerical model using a spectral micromechanical solver based on fast Fourier transform algorithms is developed to study the effects of elastic stiffness spatial heterogeneities and/or porosity on shear localization and mechanical response of metallic glasses. The model is applied to Vitreloy 1 material system. In the model, the activation rate...

Twinning is a key deformation mechanism in hexagonal close-packed (hcp) metals, which are typified by a lack of easily activated slip systems that can accommodate a general state of loading. Pragmatically, the nucleation and evolution of twin domains occurs concomitantly with slip, such that the eventual twin network is conditioned by both external and internal...

Over low and intermediate strain rates, plasticity in face centered cubic (FCC) metals is governed by the glide of dislocations, which manifest as complex networks that evolve with strain. Considering the elastic anisotropy of FCC metals, the characteristics of dislocation motion are also anisotropic (i.e. dislocation character angle-dependent), which is expected to notably influence the...

Diffusionless transformations (DTs), such as twinning, are key plastic deformation modes in metals with a limited number of slip systems. DTs can simultaneously confer excellent strength and ductility to these materials under thermomechanical loads. The efficiency of DTs is fundamentally governed by the balance between plastic dissipation (as the domains grow) and the buildup of...

Over the past several decades, there have been significant advances in our ability to predict the mechanical response and microstructure evolution of metals during deformation. Advances in experimental characterization techniques have made possible the development of physically-and mechanism-based models while, at the same time, providing stringent benchmarks to those same models.My postdoc at Los Alamos...

This work addresses the formation of adjoining twin pairs (ATPs) at grain boundaries (GBs) in hexagonal close-packed (hcp) metals from the perspective of the co-nucleation (CN) of pairs of deformation twins. A continuum defect mechanics model is proposed to investigate the energetic feasibility of the CN of ATPs resulting from the dissociation of GB dislocations....

Precipitation strengthening is a key strategy for improving the overall mechanical properties of Mg alloys. In Mg-Al alloys, basal precipitates are known to strengthen against twinning, resulting in an increase in the critical resolved shear stress (CRSS) necessary for continued deformation. Although several models have been proposed to quantify the influence of precipitate shape, size,...

This work demonstrates how the structure of a grain boundary (GB) and its evolution due to slip transmission history influences subsequent dislocation transmission. First, a model for the evolution of stress fields within grain boundaries that accounts for the effects of coherent dislocation transmission is introduced. Starting with a disclination-based construct of GBs at minimum...

Non-destructive evaluation of plastically deformed metals, particularly diffraction line profile analysis (DLPA), is valuable both to estimate dislocation densities and arrangements and to validate microstructure-aware constitutive models. To date, the interpretation of whole line diffraction profiles relies on the use of semi-analytical models such as the extended convolutional multiple whole profile (eCMWP) method. This study...

This study presents an approach to investigate the influence of intergranular stresses induced by equilibrium and non-equilibrium grain boundaries (GBs) on dislocation transmission via the discrete dislocation dynamics simulation method. First, a disclination-based construct is used to describe the equilibrium intergranular stress fields of two symmetric tilt GBs. Then, slip transfer through these GBs is...