Achieving mastery over the synthesis of metal nanocrystals has emerged as one of the foremost scientific endeavors in recent years. This intense interest stems from the fact that the composition, size, and shape of nanocrystals not only define their overall physicochemical properties but also determine their effectiveness in technologically important applications. Our aim is to present a comprehensive review of recent research activities on bimetallic nanocrystals. We begin with a brief introduction to the architectural diversity of bimetallic nanocrystals, followed by discussion of the various synthetic techniques necessary for controlling the elemental ratio and spatial arrangement. We have selected key examples from the literature that exemplify critical concepts and place a special emphasis on mechanistic understanding. We then discuss the composition-dependent properties of bimetallic nanocrystals in terms of catalysis, optics, and magnetism and conclude the Review by highlighting applications that h...

Bimetallic Nanocrystals: Syntheses, Properties, and Applications

A significant increase in the research activity dedicated to high manganese TWIP steels has occurred during the past five years, motivated by the breakthrough combination of strength and ductility possessed by these alloys. Here a review of the relations between microstructure and mechanical properties is presented focusing on plasticity mechanisms, strain-hardening, yield stress, texture, fracture and fatigue. This summarized knowledge explains why TWIP steel metallurgy is currently a topic of great practical interest and fundamental importance. Finally, this publication indicates some of the main avenues for future investigations required in order to sustain the quality and the dynamism in this field.

High manganese austenitic twinning induced plasticity steels: A review of the microstructure properties relationships

Deformation twinning in nanocrystalline materials

Twinning-induced plasticity (TWIP) steels

High entropy alloys: A focused review of mechanical properties and deformation mechanisms

https://html.mechse.illinois.edu/files/2014/08/Predicting-twinning-stress-in-fcc-metals-linking-twin-energy-pathways-to-twin-nucleation.pdf

Predicting twinning stress in fcc metals: Linking twin-energy pathways to twin nucleation

http://html.mechse.illinois.edu/files/imported/135.20080418.480913aa415448.63964000.pdf

Effect of nitrogen on generalized stacking fault energy and stacking fault widths in high nitrogen steels

We report ab initio density functional theory calculations of generalized planar fault energies of fcc Cu–xAl (x=0, 5.0, and 8.3at.%) alloys. We investigate the effects of substitutional solute Al on the unstable intrinsic γus and twin γut stacking fault energies (SFEs). Our results reveal an increased tendency of Cu–Al to deform preferentially by twinning with increasing Al content, consistent with experiment. We attribute this mechanical behavior to appreciable lowering of the twinning barrier γut, along with the stable intrinsic and twin SFEs.

/pdf/generalized-planar-fault-energies-and-twinning-in-cu-al-492ncmxzzf.pdf

Generalized planar fault energies and twinning in Cu–Al alloys

Twinning is one of most prevalent deformation mechanisms in materials. Having established a quantitative theory to predict onset twinning stress ${\ensuremath{\tau}}_{\text{crit}}$ in fcc elemental metals from their generalized planar-fault-energy (GPFE) surface, we exemplify its use in alloys where the Suzuki effect (i.e., solute energetically favors residing at and near planar faults) is operative; specifically, we apply it in $\text{Cu-}x\text{Al}$ ($x$ is 0, 5, and $8.3\text{ }\text{at}\text{.}\text{ }%$) in comparison with experimental data. We compute the GPFE via density-functional theory, and we predict the solute dependence of the GPFE and ${\ensuremath{\tau}}_{\text{crit}}$, in agreement with measured values. We show that ${\ensuremath{\tau}}_{\text{crit}}$ correlates monotonically with the unstable twin fault energies (the barriers to twin nucleation) rather than the stable intrinsic stacking-fault energies typically suggested. We correlate the twinning behavior and electronic structure with changes in solute content and proximity to the fault planes through charge-density redistribution at the fault and changes to the layer- and site-resolved density of states, where increased bonding charge correlates with decrease in fault energies and ${\ensuremath{\tau}}_{\text{crit}}$.

https://html.mechse.illinois.edu/files/imported/160.20090926.4abebcb99a4649.17671646.pdf

Quantitative prediction of twinning stress in fcc alloys: Application to Cu-Al

We present ab initio density functional theory calculations of twinning energy pathways for two opposite twinning modes, (111)[112¯] and (111)[1¯1¯2], in fcc materials to examine the directional nature of twinning which cannot be explained by classical twin nucleation models or the “twinnability” criterion. By accounting for these energy pathways in a multiscale model, we quantitatively predict the critical twinning stress for the (111)[1¯1¯2] mode to be substantially higher compared to the favorable (111)[112¯] mode (whose predicted stresses are in agreement with experiment), thus, ruling out twinning in the (111)[1¯1¯2] mode.

/pdf/energy-pathways-and-directionality-in-deformation-twinning-2ppvc7ep7z.pdf

S. Kibey

Papers

Predicting twinning stress in fcc metals: Linking twin-energy pathways to twin nucleation

Effect of nitrogen on generalized stacking fault energy and stacking fault widths in high nitrogen steels

Generalized planar fault energies and twinning in Cu–Al alloys

Quantitative prediction of twinning stress in fcc alloys: Application to Cu-Al

Energy pathways and directionality in deformation twinning