An insight into the role of the grain boundary in plastic deformation by means of a bicrystalline pillar compression test and atomistic simulation

2013 ◽  
Vol 61 (19) ◽  
pp. 7454-7465 ◽  
Author(s):  
Nousha Kheradmand ◽  
Horst Vehoff ◽  
Afrooz Barnoush
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Compression Test ◽  
Atomistic Simulation ◽  
Insight Into

Atomistic Simulation of Grain Boundary Structure and Diffusion in B2 NiAl

1996 ◽  
Vol 458 ◽  
Author(s):  
Yuri Mishin ◽  
Diana Farkas
Keyword(s):  
Grain Boundary ◽  
Atomistic Simulation ◽  
Effective Activation Energy ◽  
Correlation Effect ◽  
Boundary Structure ◽  
Self Diffusion ◽  
Embedded Atom ◽  
Grain Boundary Structure ◽  
And Diffusion

ABSTRACTUsing embedded atom potentials and molecular statics we calculate the structure and energy of [001] tilt grain boundaries in NiAl for 25 orientations with Σ values from 5 to 185. For three structures (stoichiometric, Ni-rich and Al-rich) of the Σ = 5 (210) boundary we simulate tracer self-diffusion by the vacancy mechanism both parallel and perpendicular to the tilt axis using the Monte Carlo technique. The effective activation energy calculated in a wide temperature range is compared with the spectrum of individual jump energies in the boundary core. The results are interpreted in terms of the grain boundary structure-diffusion relationship and the role of the jump correlation effect in grain boundary diffusion.

An atomistic simulation study of nanoscale sintering: The role of grain boundary misorientation

2019 ◽  
Vol 165 ◽  
pp. 180-189 ◽  
Author(s):  
Jesse M. Sestito ◽  
Fadi Abdeljawad ◽  
Tequila A.L. Harris ◽  
Yan Wang ◽  
Allen Roach
Keyword(s):  
Grain Boundary ◽  
Simulation Study ◽  
Atomistic Simulation ◽  
Boundary Misorientation ◽  
Grain Boundary Misorientation

scholarly journals The effect of Cr alloying on defect migration at Ni grain boundaries

2022 ◽  
Author(s):  
Blas P. Uberuaga ◽  
Pauline Simonnin ◽  
Kevin M. Rosso ◽  
Daniel K. Schreiber ◽  
Mark Asta
Keyword(s):  
Grain Boundary ◽  
Mass Transport ◽  
Grain Boundaries ◽  
Experimental Studies ◽  
Boundary Mobility ◽  
Defect Migration ◽  
Grain Boundary Mobility ◽  
Tilt Boundaries ◽  
Insight Into

AbstractMass transport along grain boundaries in alloys depends not only on the atomic structure of the boundary, but also its chemical make-up. In this work, we use molecular dynamics to examine the effect of Cr alloying on interstitial and vacancy-mediated transport at a variety of grain boundaries in Ni. We find that, in general, Cr tends to reduce the rate of mass transport, an effect which is greatest for interstitials at pure tilt boundaries. However, there are special scenarios in which it can greatly enhance atomic mobility. Cr tends to migrate faster than Ni, though again this depends on the structure of the grain boundary. Further, grain boundary mobility, which is sometimes pronounced for pure Ni grain boundaries, is eliminated on the time scales of our simulations when Cr is present. We conclude that the enhanced transport and grain boundary mobility often seen in this system in experimental studies is the result of non-equilibrium effects and is not intrinsic to the alloyed grain boundary. These results provide new insight into the role of grain boundary alloying on transport that can help in the interpretation of experimental results and the development of predictive models of materials evolution.

Atomistic Studies of Intrinsic Crack-Tip Plasticity

MRS Bulletin ◽  
2000 ◽  
Vol 25 (5) ◽  
pp. 35-38 ◽  
Author(s):  
Diana Farkas
Keyword(s):  
Plastic Deformation ◽  
Energy Dissipation ◽  
Atomistic Simulation ◽  
Experimental Studies ◽  
Crack Tip ◽  
Atomic Level ◽  
Simulation Studies ◽  
Precise Understanding ◽  
Crack Tip Plasticity ◽  
Insight Into

One of the most interesting unsolved problems in fracture mechanics is the precise understanding of the energy-dissipation mechanisms that occur as a crack advances. In most cases, this energy-release rate is many times the surface energy created. One of the main reasons for this difference is the fact that plastic deformation can occur in the crack-tip region as dislocations nucleate and are emitted from the crack tip. Experimental studies provide little insight into the precise mechanisms for this process because they cannot reach the atomistic scale. For example, a crack that may seem experimentally sharp, and therefore indicative of brittle fracture, may not be sharp at the atomic level. Continuum mechanics has a similar limitation, since the assumptions of elasticity theory usually break down in the crack-tip region. Atomistic simulation studies provide researchers an opportunity to obtain precise atomic configurations in the crack-tip region under various loading conditions and to observe the basic energy-dissipation mechanisms.

Processing Metals by Severe Plastic Deformation

2005 ◽  
Vol 101-102 ◽  
pp. 13-22 ◽  
Author(s):  
Andrzej Rosochowski
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Material Flow ◽  
Historical Development ◽  
Coarse Grain ◽  
Commercial Use ◽  
Ultrafine Grained ◽  
Mechanical And Physical Properties ◽  
Insight Into

Severe plastic deformation (SPD) is used to convert traditional coarse grain metals and alloys into ultrafine-grained (UFG) materials. UFG materials possess a number of improved mechanical and physical properties which destine them for a wide commercial use. However, any attempt to use SPD technology commercially requires a better insight into the mechanics and practicality of SPD processes. This paper looks into historical development of SPD processes and focuses on such aspects of SPD as material flow, role of hydrostatic pressure, friction, geometry of tools, billet and feeding considerations, technical feasibility, etc. The discussion of these topics sets a background for decisions concerning further research and commercialisation of SPD.

Atomistic Modeling of Grain Boundaries and Dislocation Processes in Metallic Polycrystalline Materials

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Douglas E. Spearot ◽  
David L. McDowell
Keyword(s):  
Plastic Deformation ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Behavior ◽  
Complex Stress ◽  
Boundary Structure ◽  
Polycrystalline Materials ◽  
Atomistic Modeling ◽  
Triple Junctions

The objective of this review article is to provide a concise discussion of atomistic modeling efforts aimed at understanding the nanoscale behavior and the role of grain boundaries in plasticity of metallic polycrystalline materials. Atomistic simulations of grain boundary behavior during plastic deformation have focused mainly on three distinct configurations: (i) bicrystal models, (ii) columnar nanocrystalline models, and (iii) 3D nanocrystalline models. Bicrystal models facilitate the isolation of specific mechanisms that occur at the grain boundary during plastic deformation, whereas columnar and 3D nanocrystalline models allow for an evaluation of triple junctions and complex stress states characteristic of polycrystalline microstructures. Ultimately, both sets of calculations have merits and are necessary to determine the role of grain boundary structure on material properties. Future directions in grain boundary modeling are discussed, including studies focused on the role of grain boundary impurities and issues related to linking grain boundary mechanisms observed via atomistic simulation with continuum models of grain boundary plasticity.

Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

1991 ◽  
Vol 49 ◽  
pp. 604-605
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D. Matlock
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Deformation Twin ◽  
Austenitic Stainless Steels ◽  
Carbide Precipitation ◽  
Strain Induced Martensite ◽  
Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

On the role of tin underlays for the prevention of thermal grooving in thin gold films

1986 ◽  
Vol 44 ◽  
pp. 732-733
Author(s):  
Jin Young Kim ◽  
R. E. Hummel ◽  
R. T. DeHoff
Keyword(s):  
Thin Film ◽  
Free Surface ◽  
Grain Boundary ◽  
Beneficial Effect ◽  
Failure Mechanism ◽  
Failure Mechanisms ◽  
Distinct Advantage ◽  
Gold Films ◽  
Gold Thin Film

Gold thin film metallizations in microelectronic circuits have a distinct advantage over those consisting of aluminum because they are less susceptible to electromigration. When electromigration is no longer the principal failure mechanism, other failure mechanisms caused by d.c. stressing might become important. In gold thin-film metallizations, grain boundary grooving is the principal failure mechanism.Previous studies have shown that grain boundary grooving in gold films can be prevented by an indium underlay between the substrate and gold. The beneficial effect of the In/Au composite film is mainly due to roughening of the surface of the gold films, redistribution of indium on the gold films and formation of In2O3 on the free surface and along the grain boundaries of the gold films during air annealing.

Plasminogen Activation In Vivo upon Intravenous Infusion of DDAVP

1992 ◽  
Vol 67 (01) ◽  
pp. 111-116 ◽  
Author(s):  
Marcel Levi ◽  
Jan Paul de Boer ◽  
Dorina Roem ◽  
Jan Wouter ten Cate ◽  
C Erik Hack
Keyword(s):  
Monoclonal Antibodies ◽  
Plasminogen Activator ◽  
Plasma Levels ◽  
Fold Increase ◽  
Fibrinolytic System ◽  
Plasminogen Activation ◽  
Plasminogen Activator Activity ◽  
Insight Into

SummaryInfusion of desamino-d-arginine vasopressin (DDAVP) results in an increase in plasma plasminogen activator activity. Whether this increase results in the generation of plasmin in vivo has never been established.A novel sensitive radioimmunoassay (RIA) for the measurement of the complex between plasmin and its main inhibitor α2 antiplasmin (PAP complex) was developed using monoclonal antibodies preferentially reacting with complexed and inactivated α2-antiplasmin and monoclonal antibodies against plasmin. The assay was validated in healthy volunteers and in patients with an activated fibrinolytic system.Infusion of DDAVP in a randomized placebo controlled crossover study resulted in all volunteers in a 6.6-fold increase in PAP complex, which was maximal between 15 and 30 min after the start of the infusion. Hereafter, plasma levels of PAP complex decreased with an apparent half-life of disappearance of about 120 min. Infusion of DDAVP did not induce generation of thrombin, as measured by plasma levels of prothrombin fragment F1+2 and thrombin-antithrombin III (TAT) complex.We conclude that the increase in plasminogen activator activity upon the infusion of DDAVP results in the in vivo generation of plasmin, in the absence of coagulation activation. Studying the DDAVP induced increase in PAP complex of patients with thromboembolic disease and a defective plasminogen activator response upon DDAVP may provide more insight into the role of the fibrinolytic system in the pathogenesis of thrombosis.

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