arXiv subjects

Jason R. Trelewicz

Publications and source records attributed to Jason R. Trelewicz.

10 recordsLinked to original sources

arXiv2026

Synergistic doping of the grain interior and grain boundary alters deformation mechanisms and enables extreme strength in nanocrystalline Ni-Cr-Y alloys

Solid solution addition and grain boundary segregation have been independently shown to enhance the strength of nanocrystalline alloys. In the present study, the interplay between these two effects is investigated in nanocrystalline Ni-Cr-Y sputtered films through systematic variation of alloying element contents with grain size kept constant. Cr is introduced into a solid solution and serves to strengthen the lattice, while Y segregates to the grain boundaries to stabilize these features. Nanoindentation is used to probe hardness, with unexpected trends and very high values observed. Cr additions led to nanocrystalline solid solution strengthening, yet saturation was observed at higher concentrations due to the emergence of grain boundary dominated processes, as evidenced by pile-up morphologies containing slip steps and grain rotation. Y enrichment was observed at the examined grain boundaries, enhancing boundary-mediated strengthening by pinning the dislocations and suppressing dislocation emission, grain boundary sliding, and grain rotation processes. With increasing Y concentration, the nanocrystalline solid solution strengthening effect induced by Cr addition becomes weaker. This phenomenon can be attributed to a reduced dislocation bowing distance caused by dopant pinning. Most notably, the strongest ternary Ni-Cr-Y alloy exhibited a hardness of 11.0 GPa, among the highest hardness values reported for single-phase nanocrystalline Ni alloys with grain sizes near 20 nm. These findings highlight how tuning grain and grain boundary chemistry offers a viable strategy to control dislocation mechanics and improve the strength of nanocrystalline metals.

cond-mat.mtrl-sci↗

arXiv2026

Grain Boundary Defect Production during Successive Displacement Cascades on a Tungsten Surface

The interaction of radiation defects with grain boundaries (GBs) governs damage tolerance in refractory materials for extreme environments. Tungsten (W), a leading plasma-facing material for fusion, will be subjected to coupled ion and neutron irradiation that degrades both surface and bulk properties. In this study, molecular dynamics (MD) simulations are employed to examine defect evolution under successive 1 keV displacement cascades at a W surface in nano-bicrystals containing Sigma3 and Sigma5 symmetric tilt GBs. The free surface biases interstitial accumulation toward surface planes, reducing bulk interstitial populations, while vacancy saturation is driven by cascade overlap. When cascades indirectly interact with GBs, defect accumulation becomes strongly dependent on GB character. The higher energy Sigma5 boundary acts as a more effective defect sink for interstitials relative to the coherent Sigma3 boundary. This behavior arises from its larger interstitial segregation energy and enhanced strain field, which promote trapping via thermal migration and focused collision sequences. The deeper trap states of the Sigma5 GB suppress interstitial emission and limit recovery, whereas the shallower traps and mobile crowdion configurations in Sigma3 GBs enable dynamic defect recombination. These results highlight the critical role of GB structure and grain size in controlling radiation damage evolution in tungsten with behavior that applies broadly to refractory BCC metals.

cond-mat.mtrl-sci↗

arXiv2026

A computational alloy design framework for the promotion of amorphous grain boundary complexions

Amorphous grain boundary complexions have been shown to be radiation tolerant interfaces that can also reduce grain boundary embrittlement, marking them as favorable microstructural features. However, the incorporation of these features into new alloy systems is often a slow and arduous process based on trial and error. Here, a computational framework for alloy design is presented which enables the selection of dopants that promote the formation of amorphous grain boundary complexions. This framework is primarily built on density functional theory calculations and is demonstrated for W-rich binary and ternary alloys, which represent a promising target for fusion energy materials. Our framework first evaluates the grain boundary segregation tendency of dopants and then the energy penalty for amorphization alongside targeted interfacial energy comparison, with the end goal of identifying the best dopants. For a W base, Y and some transition metals such as Co and Ni are found to significantly lower these energetic barriers. Electronic structure analysis, local lattice distortion, and charge density distributions are calculated and used to provide mechanistic explanations for these dopant selections. Finally, the framework is validated by comparing with experimental literature for W alloys and a refractory complex concentrated alloy, showing a strong correlation between our dopant selections and low sintering onset temperatures that have been attributed to activated sintering. As a whole, this work establishes a transferable pipeline for designing alloys with grain-boundary complexions across diverse alloy systems.

cond-mat.mtrl-sci↗

arXiv2026

Irradiation-Driven Recrystallization in Fusion-Grade Tungsten: A Mesoscale, Microstructure-Aware Model

Tungsten (W) is the leading candidate material for plasma-facing components in fusion reactors, yet its upper operational temperature is limited by premature grain growth and recrystallization processes. Irradiation adds further complications by generating defect clusters and transmutation products that alter both the driving forces and kinetics of grain boundary motion. In this work, we develop a physics-based, multiscale framework that couples crystal plasticity, stochastic cluster dynamics, and discrete grain boundary dynamics to model the co-evolution of plastic deformation, irradiation damage, and grain growth in fusion-grade tungsten polycrystals. The approach enables simulations on realistic microstructures with arbitrary grain size and misorientation distributions, without recourse to mean-field simplifications. The model captures (i) the spatial heterogeneity of dislocation density distribution during hot working; (ii) irradiation-induced defect accumulation under fusion conditions, and (iii) the buildup of chemical and elastic driving forces for grain boundary migration and microstructural evolution. Parametric studies demonstrate the dominant influence that temperature has on thermally activated grain-boundary mobility, a weaker dependence on prior strain, and a pronounced retardation of recrystallization by rhenium segregation arising from neutron transmutation. Under fusion energy irradiation conditions, our framework predicts a substantial reduction of the effective recrystallization temperature relative to unirradiated microstructures, while Re production restores and even elevates this limit. By providing quantitative projections of recrystallization kinetics and in-service recrystallization temperatures, this work establishes a predictive tool for assessing the lifetime and operational envelope of W-based plasma-facing materials under fusion conditions.

cond-mat.mtrl-sci↗

arXiv2025

Grain Boundary Anisotropy and Its Influence on Helium Bubble Nucleation, Growth, and Decohesion in Polycrystalline Iron

The accumulation of helium bubbles at grain boundaries (GBs) critically degrades the mechanical integrity of structural materials in nuclear reactors. While GBs act as sinks for radiation-induced defects, their inherent structural anisotropy leads to complex helium bubble evolution behaviors that remain poorly understood. This work integrates accelerated molecular dynamics simulations and a novel atomic-scale metric, the flexibility volume (V_f), to establish the interplay between GB character, helium segregation, and bubble growth mechanisms in body-centered cubic iron. We demonstrate that V_f, which incorporates both local atomic volume and vibrational properties, qualitatively predicts deformation propensity. Our results reveal that the atomic-scale segregation energy landscape dictates initial helium clustering and subsequent bubble morphology, with low-energy channels in tilt Σ5 boundary facilitating one-dimensional migration while isolated deep traps in twist Σ13 boundary promote larger, rounder bubble morphology. Critically, besides gradual bubble growth via trap mutation mechanism, we identify two distinct stress-relief mechanisms: loop punching in anisotropic tilt Σ5 boundary and interfacial decohesion in twist Σ11 boundary, with the dominant pathway determined by the interplay between bubble morphology and local mechanical softness. This study establishes a fundamental connection between GB crystallographic and energetical anisotropy and helium bubble evolution, providing critical insights for designing radiation-tolerant microstructures.

cond-mat.mtrl-sci↗

arXiv2024

Primary Defect Production in Doped Iron Grain Boundaries during Low Energy Collision Cascades

This study explores the intricate interactions between grain boundaries (GBs) and irradiation-induced defects in nanocrystalline iron, highlighting the role of dopants like copper. Utilizing molecular dynamics simulations, the research delineates how GB properties, such as GB energy and defect formation energies, influence the formation and evolution of defects in low energy collision cascades. It reveals that GBs not only augment defect production but also show a marked preference for interstitials over vacancies, a behavior significantly modulated by the cascade's proximity to the GB. The presence of dopants is shown to alter GB properties, affecting both the rate and type of defect production, thereby underscoring the complex interplay between GB characteristics, dopant elements, and defect dynamics. Moreover, the investigation uncovers that the structural characteristics of GBs play a crucial role in cascade evolution and defect generation, with certain GB configurations undergoing reconfiguration in response to cascades. For instance, the reconfiguration of one pure Fe twist GB suggests that GB geometry can significantly influence defect generation mechanisms. These findings point to the potential of GB engineering in developing materials with enhanced radiation tolerance, advocating for a nuanced approach to material design. By tailoring GB properties and selectively introducing dopant elements, materials can be optimized to exhibit superior resistance to radiation-induced damage, offering insights for applications in nuclear reactors and other radiation-prone environments.

cond-mat.mtrl-sci↗

arXiv2024

The Role of Temperature on Irradiation Defect Evolution near Surfaces and Grain Boundaries in Tungsten

This study explores the impact of temperature on defect dynamics in tungsten, emphasizing its application in nuclear fusion reactors as Plasma Facing Components (PFCs). Through atomistic simulations, the research elucidates the intricate interplay of defect production, annihilation, and redistribution under irradiation at room (300K) and elevated temperatures (1000K). It demonstrates that higher temperatures significantly increase the number and mobility of defects, leading to a substantial rise in the total number of surviving Frenkel Pairs (FPs), with a notable preference for surface distribution. This redistribution is attributed to energy gradient-driven relocation processes, enhanced by the defects' increased mobility at elevated temperatures. Moreover, the study reveals that elevated temperatures promote biased accumulation of interstitial defects in grain boundaries, especially in configurations that facilitate efficient interstitial migration, indicating a strategy for minimizing lattice interstitial accumulation under irradiation. These findings underscore the critical role of temperature in modulating irradiation-induced defect dynamics in tungsten, providing valuable insights for designing and selecting materials with optimized irradiation resistance for use in extreme conditions of nuclear fusion reactors. The research suggests a material design approach that accounts for temperature effects to enhance the durability and performance of nuclear fusion materials.

cond-mat.mtrl-sci↗

arXiv2023

Enhanced radiation damage tolerance of amorphous interphase and grain boundary complexions in Cu-Ta

Amorphous interfacial complexions are particularly resistant to radiation damage and have been primarily studied in alloys with good glass-forming ability, yet recent reports suggest that these features can form even in immiscible alloys such as Cu-Ta under irradiation. In this study, the mechanisms of damage production and annihilation due to primary knock-on atom collisions are investigated for amorphous interphase and grain boundaries in a Cu-Ta alloy using atomistic simulations. Amorphous complexions, in particular amorphous interphase complexions that separate Cu and Ta grains, result in less residual defect damage than their ordered counterparts. Stemming from the nanophase chemical separation in this alloy, the amorphous complexions exhibit a highly heterogeneous distribution of atomic excess volume, as compared to a good glass former like Cu-Zr. Complexion thickness, a tunable structural descriptor, plays a vital role in damage resistance. Thicker interfacial films are more damage-tolerant because they alter the defect production rate due to differences in intrinsic displacement threshold energies during the collision cascade. Overall, the findings of this work highlight the importance of interfacial engineering in enhancing the properties of materials operating in radiation-prone environments and the promise of amorphous complexions as particularly radiation damage-tolerant microstructural features.

cond-mat.mtrl-sci↗

arXiv2023

Alloying Effects on the Microstructure and Properties of Laser Additively Manufactured Tungsten Materials

A large body of literature within the additive manufacturing (AM) community has focused on successfully creating stable tungsten (W) microstructures due to significant interest in its application for extreme environments. However, solidification cracking and additional embrittling features at grain boundaries have resulted in poorly performing microstructures, stymying the application of AM as a manufacturing technique for W. Several alloying strategies, such as ceramic particles and ductile elements, have emerged with the promise to eliminate solidification cracking while simultaneously enhancing stability against recrystallization. In this work, we provide new insights regarding the defects and microstructural features that result from the introduction of ZrC for grain refinement and NiFe as a ductile reinforcement phase - in addition to the resulting thermophysical and mechanical properties. ZrC is shown to promote microstructural stability with increased hardness due to the formation of ZrO2 dispersoids. Conversely, NiFe forms into micron-scale FCC phase regions within a BCC W matrix, producing enhanced toughness relative to pure AM W. A combination of these effects is realized in the WNiFe+ZrC system and demonstrates that complex chemical environments coupled with the tuning of AM microstructures provides an effective pathway for enabling laser AM W materials with enhanced stability and performance.

cond-mat.mtrl-sci↗

arXiv2017

Nanocrystalline Al-Mg with extreme strength due to grain boundary doping

Nanocrystalline Al-Mg alloys are used to isolate the effect of grain boundary doping on the strength of nanostructured metals. Mg is added during mechanical milling, followed by low homologous temperature annealing treatments to induce segregation without grain growth. Nanocrystalline Al -7 at.% Mg that is annealed for 1 h at 200 °C is the strongest alloy fabricated, with a hardness of 4.56 GPa or approximately three times that of pure nanocrystalline Al. Micropillar compression experiments indicate a yield strength of 865 MPa and a specific strength of 329 kN m/kg, making this one of the strongest lightweight metals reported to date.

cond-mat.mtrl-sci↗