Atomistic modeling of interfaces and their impact on microstructure and properties

Mishin, Y.; Asta, Mark; Li, Ju

doi:10.1016/j.actamat.2009.10.049

Cited by 458 publications

(292 citation statements)

References 615 publications

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“…Interfaces play a fundamental role in determining the properties of materials [1][2][3]. This is particularly true in regard to their effect on the mechanical behaviour of multi-phase alloy systems.…”

Section: Introductionmentioning

confidence: 99%

Coarsening behaviour and interfacial structure of γ′ precipitates in Co-Al-W based superalloys

Vorontsov¹,

Barnard

Rahman³

et al. 2016

Acta Materialia

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This work discusses the effects of alloying on the coarsening behaviour of the L1 2 ordered γ phase and the structure of the γ/γ interfaces in three Co-Al-W base superalloys aged at ∼90 • C below the respective solvus temperatures: Co-7Al-7W, Co10Al-5W-2Ta and Co-7Al-7W-20Ni (at.%). The coarsening kinetics are adequately characterised by the classical Lifshitz-Slyozov-Wagner model for Ostwald ripening. Co-7Al-7W exhibited much slower coarsening than its quaternary derivatives. Alloying can be exploited to modify the coarsening kinetics either by increasing the solvus temperature by adding tantalum, or by adding nickel to shift the rate controlling mechanism towards dependence on the diffusion of aluminium rather than tungsten. Lattice resolution STEM imaging was used to measure the widths of the order-disorder (structural) and Z-contrast (compositional) gradients across the γ/γ interfaces. Similarly to nickel base superalloys, the compositional gradient was found to be wider than the structural. Co-7Al-7W-20Ni had much wider interface gradients than Co-7Al-7W and Co-10Al-5W-2Ta, which suggests that its γ phase stoichiometry is less constrained. A possible correlation between temperature and misfit normalised r vs. t 1 3 coarsening rate coefficients and the structural gradient width has also been identified, whereby alloys with wider interfaces exhibit faster coarsening rates.

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Section: Introductionmentioning

confidence: 99%

Coarsening behaviour and interfacial structure of γ′ precipitates in Co-Al-W based superalloys

Vorontsov¹,

Barnard

Rahman³

et al. 2016

Acta Materialia

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“…Structural transformations at grain boundaries (GBs) are of fundamental interest and can have a significant impact on microstructure, mechanical behavior and transport properties of polycrystalline materials [1,2]. A number of GB phases have been found in alloys [3] and ceramic materials [4,5], where they often appear in the form of intergranular thin films and are referred to as "complexions" [6].…”

Section: Introductionmentioning

confidence: 99%

“…Much of the current knowledge about GB structures comes from atomistic computer simulations [1,2]. Many previous simulations have shown a behavior where GBs exhibit structural disorder at high temperatures and eventually melt by either turning into a continuously growing liquid film or triggering bulk melting [1,2,15,18,19].…”

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confidence: 99%

Effect of Interface Phase Transformations on Diffusion and Segregation in High-Angle Grain Boundaries

2013

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Recent experimental measurements of Ag impurity diffusion in the Σ5 (310) grain boundary (GB) in Cu revealed an unusual non-Arrhenius behavior suggestive of a possible structural transformation [Divinski et al., Phys. Rev. B 85, 144104 (2012)]. On the other hand, atomistic computer simulations have recently discovered phase transformations in high-angle GBs in metals [Frolov et al., Nature Communications, 4, 1899(2013]. In this paper we report on atomistic simulations of Ag diffusion and segregation in two different structural phases of the Cu Σ5 (310) GB which transform to each other with temperature. The obtained excellent agreement with the experimental data validates the hypothesis that the unusual diffusion behavior seen in the experiment was caused by a phase transformation. The simulations also predict that the low-temperature GB phase exhibits a monolayer segregation pattern while the high-temperature phase features a bilayer segregation. Together, the simulations and experiment provide the first convincing evidence for the existence of structural phase transformations in high-angle metallic GBs and demonstrate the possibility of their detection by GB diffusion measurements and atomistic simulations.Motivation. Structural transformations at grain boundaries (GBs) are of fundamental interest and can have a significant impact on microstructure, mechanical behavior and transport properties of polycrystalline materials [1,2]. A number of GB phases have been found in alloys [3] and ceramic materials [4,5], where they often appear in the form of intergranular thin films and are referred to as "complexions" [6]. In metallic alloys, several phases with discrete thickness have been observed, such as the segregated bilayer structure believed to be responsible for the liquid-layer embrittlement effect [7]. However, despite

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“…Ref. 30) V (W ) = ∆γ exp(−W/δ), (2) where ∆γ = γ gb − 2γ sl is the difference between the GB energy (γ gb ) and the excess free-energy of two separated solid-liquid interfaces (2γ sl ). Substitution of this form into Eq.…”

Section: Introductionmentioning

confidence: 99%

Phase-field-crystal study of grain boundary premelting and shearing in bcc iron

et al. 2013

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We use the phase-field-crystal (PFC) method to investigate the equilibrium premelting and nonequilibrium shearing behaviors of [001] symmetric tilt grain boundaries (GBs) at high homologous temperature over the complete range of misorientation 0 < θ < 90 • in classical models of bcc Fe. We characterize the dependence of the premelted layer width W as a function of temperature and misorientation. In addition, we compute the thermodynamic disjoining potential whose derivative with respect to W represents the structural force between crystal-melt interfaces due to the spatial overlap of density waves. The disjoining potential is also computed by molecular dynamics (MD) simulations, for quantitative comparison with PFC simulations, and coarse-grained amplitude equations (AE) derived from PFC that provide additional analytical insights. We find that, for GBs over an intermediate range of misorientation (θmin < θ < θmax), W diverges as the melting temperature is approached from below, corresponding to a purely repulsive disjoining potential, while for GBs outside this range (θ < θmin or θmax < θ < 90 • ), W remains finite at the melting point. In the latter case, W corresponds to a shallow attractive minimum of the disjoining potential. The misorientation range where W diverges predicted by PFC simulations is much smaller than the range predicted by MD simulations when the small dimensionless parameter ǫ of the PFC model is matched to liquid structure factor properties. However it agrees well with MD simulations with a lower ǫ value chosen to match the ratio of bulk modulus and solid-liquid interfacial free-energy, consistent with the amplitude-equation prediction that θmin and 90 • − θmax scale as ∼ ǫ 1/2 . The incorporation of thermal fluctuations in PFC is found to have a negligible effect on this range. In response to a shear stress parallel to the GB plane, GBs in PFC simulations exhibit coupled motion normal to this plane or sliding. Furthermore, the coupling factor exhibits a discontinuous change as a function of θ that reflects a transition between two coupling modes. Sliding is only observed over a range of misorientation that is a strongly increasing function of temperature for T /TM ≥ 0.8 and matches roughly the range where W diverges at the melting point. The coupling factor for the two coupling modes is in excellent quantitative agreement with previous theoretical predictions [J. W. Cahn, Y. Mishin, and A. Suzuki, Acta Mater. 54, 4953 (2006)].

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Atomistic modeling of interfaces and their impact on microstructure and properties

Cited by 458 publications

References 615 publications

Coarsening behaviour and interfacial structure of γ′ precipitates in Co-Al-W based superalloys

Coarsening behaviour and interfacial structure of γ′ precipitates in Co-Al-W based superalloys

Effect of Interface Phase Transformations on Diffusion and Segregation in High-Angle Grain Boundaries

Phase-field-crystal study of grain boundary premelting and shearing in bcc iron

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