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Alloy 693 is a precipitation hardenable nickel base superalloy containing about 30% Cr, 4% Fe, 4% Al, 1.5% Nb and 0.3% Ti (in wt.%). At elevated temperatures, alloy precipitates out particles of an ordered γ′ phase (L12 crystal structure) with Ni3(Al,Ti,Nb) stoichiometry. These particles remain coherent and maintain a cube-to-cube orientation relationship with the face-centered cubic matrix. The alloy also has a tendency to form chromium-rich α phase (body-centered cubic crystal structure) particles at temperatures above 800 °C. The α phase particles maintain a Kurdjumov–Sachs orientation relationship with the matrix. This paper reports the effect of the precipitation of γ′ and α phases on the residual stresses developed in the alloy, and correlates them with the misfit strains due to the precipitation of the two phases. Residual stresses have been measured using the blind hole drilling method, while the misfit strains have been calculated based on the lattice parameters of matrix, γ′ and α phases determined using neutron diffraction. The precipitation of the γ′ phase introduces tensile nature of stresses in the matrix, while that of the α phase introduces compressive stresses. The overall nature of the residual stresses in the alloy is governed by the volume fraction of the two precipitates. [ABSTRACT FROM AUTHOR]

Stoney formula is widely used in advanced devices to estimate the residual stress of thin film/substrate system by measuring surface curvature. Many hypotheses including that thin film thickness is ignored are required, thus bringing significant error in characterizing the inhomogeneous residual stress distribution. In this article, arbitrary residual stresses on thin film/substrate structures with nonnegligible film thickness are modeled and characterized. We introduce nonuniform misfit strain and establish the governing equations including mismatched strain, displacements, and interfacial stresses based on the basic elastic theory. The parameterization method and the method of constant variation are used in the process of equation decoupling. The expressions between displacements, surface curvatures, and misfit strain are determined through decoupling calculations. By substituting misfit strain, residual stresses are expressed by parametric equation related to surface curvature. It further indicates that there is a "non-local" part between the film stress and curvature at the same point. Compared to neglecting the film thickness, the proposed method eliminate relative errors up to 58.3%, which is of great significance for stress measurement of thin films and substrates. [ABSTRACT FROM AUTHOR]

Cycling-induced cathode interfacial degradations are usually attributed to chemical process, while the physical effect is overlooked to a large extent. Herein, we investigate the failure mechanism of LiCoO2 cathode and reveal that misfit strain plays a dominant role in the surface layer exfoliation process. We illustrate that highly strained LiCoO2 surface can initiate massive surface cracks, leading to the LiCoO2 surface layer broken and exfoliation. Mechanical cracking coupled with chemical etching aggravates the surface layer degradation, leading to a weathering-like degradation on LiCoO2 surface. Our work reveals that interfacial degradation of electrode materials is a complex physicochemical process.Impact StatementInterfacial degradations are usually believed as chemical effect dominated failure. Herein, we show that the overlooked physical effect, misfit strain, in fact plays a critical role in the surface degradation process and stress that LiCoO2 surface degradation is a complex physicochemical process.

Cycling-induced cathode interfacial degradations are usually attributed to chemical process, while the physical effect is overlooked to a large extent. Herein, we investigate the failure mechanism of LiCoO2 cathode and reveal that misfit strain plays a dominant role in the surface layer exfoliation process. We illustrate that highly strained LiCoO2 surface can initiate massive surface cracks, leading to the LiCoO2 surface layer broken and exfoliation. Mechanical cracking coupled with chemical etching aggravates the surface layer degradation, leading to a weathering-like degradation on LiCoO2 surface. Our work reveals that interfacial degradation of electrode materials is a complex physicochemical process. Impact Statement We declare that we have no financial and personal relationships with other people or organizations. [ABSTRACT FROM AUTHOR]

xPb(In1/2Nb1/2)O3-(1−x−y)Pb(Mg1/3Nb2/3)O3−yPbTiO3 (PIN–PMN–PT) bulks possess excellent electromechanical coupling and dielectric properties, but the corresponding epitaxial PIN–PMN–PT thin films have not yet been explored. This paper adopts a nonlinear thermodynamics analysis to investigate the influences of misfit strains on the phase structures, electromechanical properties, and electrocaloric responses in epitaxial PIN–PMN–PT thin films. The misfit strain–temperature phase diagram was constructed. The results reveal that the PIN–PMN–PT thin films may exist in tetragonal c-, orthorhombic aa-, monoclinic M-, and paraelectric PE phases. It is also found that the c-M and aa-PE phase boundaries exhibit a superior dielectric constant ε 11 which reached 1.979 × 106 with um = −0.494%, as well as the c-M phase boundary showing a large piezoelectric response d15 which reached 1.64 × 105 pm/V. In comparison, the c-PE and M-aa phase boundaries exhibit a superior dielectric constant ε33 over 1 × 105 around um = 0.316% and the piezoelectric response d33 reached 7235 pm/V. The large electrocaloric responses appear near the paraelectric- ferroelectric phase boundary. These insights offer a guidance for experiments in epitaxial PIN–PMN–PT thin films. [ABSTRACT FROM AUTHOR]

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Thin films of Y:ZrO2 (YSZ) have been grown on vicinal NdGaO3 substrates (tilted by 0º–3º around [001] NdGaO3 from (110) plane toward (010) plane) by pulsed laser deposition. The surface of the films is smooth, the signs of step-flow growth mode can be detected for small tilt angles < 0.2º. The orientation of the films followed graphoepitaxial matching with the substrates for all studied tilt angles down to 0.06º. In case of arbitrary in-plane orientation of the tilt axis, the graphoepitaxial growth mode was observed in both substrate in-plane directions. The thin YSZ films showed narrow rocking curves and contracted c lattice constant normal to the (110) plane. An increase of film thickness results in relaxation of c to 5.142 Å, in a good agreement with the bulk value for the target composition of 9 mol% Y2O3:ZrO2. The width of the rocking curve increases with thickness to a relatively high level ~ 3º. Both thickness dependences show exponential saturation with characteristic thicknesses 13–19 nm. The reason for such a behavior is probably the gradual relaxation of the substrate-induced strain with thickness by generation of dislocations. [ABSTRACT FROM AUTHOR]

Ferroelectric thin films usually exhibit polydomain structures, while current thermodynamics analysis on (1âˆ' x)Pb(Mg1/3Nb2/3)â€" x PbTiO3 [(1âˆ' x)PMNâ€" x PT] thin films assumed films only possessing single domain. Thus we predict misfit strainâ€"temperature phase diagrams and electromechanical properties of epitaxial (1âˆ' x)PMNâ€" x PT thin films via thermodynamics analysis with polydomain structures taken into account. The results show that polydomain structures are more stable than single domain in most areas, consistent well with experimental observations. Phase diagram for 0.7PMN-0.3PT thin films obviously differs from those for 0.58PMN-0.42PT and 0.3PMN-0.7PT thin films. Excellent electromechanical properties are observed near the phase boundary between c and r 1/ r 2 phases in 0.7PMN-0.3PT thin films. [ABSTRACT FROM AUTHOR]

In the present work, the effect of a thermodynamically consistent inelastic interface stress on nanovoid evolution in NiAl is studied. Such interface stress is introduced for the solid–gas interface of nanovoids within the concept of the phase field approach. The Cahn–Hilliard (CH) equation using the Helmholtz free energy describes the evolution of nanovoid concentration. The interface stress changes the total stress distribution and affects the elastic stress field. Thus, due to the significant effect of the elastic energy on nanovoid dynamics, it can indirectly affect nanovoid nucleation and growth. The highly nonlinear coupled CH and elasticity equations are solved using the finite element method and the COMSOL code. The coupling appears due to the presence of the nonlinear nanovoid inelastic strain in the total strain, the presence of the nonlinear inelastic interface stress in the stress tensor and the presence of elastic energy in the Helmholtz free energy. Several examples of thermal-induced nanovoid evolutions are presented to investigate the effect of the solid–gas interface stress. The obtained results show the significant effect of the interface stress on the total stress distribution, and consequently a different distribution of thermodynamic driving force which can affect the nanostructure evolution and the deformation. Mainly, the interface stress represents a promotive effect on nanovoid growth which results in a faster nanovoid growth and a larger nanovoid concentration and region. [ABSTRACT FROM AUTHOR]

xPb(In1/2Nb1/2)O3-(1−x−y)Pb(Mg1/3Nb2/3)O3−yPbTiO3 (PIN–PMN–PT) bulks possess excellent electromechanical coupling and dielectric properties, but the corresponding epitaxial PIN–PMN–PT thin films have not yet been explored. This paper adopts a nonlinear thermodynamics analysis to investigate the influences of misfit strains on the phase structures, electromechanical properties, and electrocaloric responses in epitaxial PIN–PMN–PT thin films. The misfit strain–temperature phase diagram was constructed. The results reveal that the PIN–PMN–PT thin films may exist in tetragonal c-, orthorhombic aa-, monoclinic M-, and paraelectric PE phases. It is also found that the c-M and aa-PE phase boundaries exhibit a superior dielectric constant ε11 which reached 1.979 × 106 with um = −0.494%, as well as the c-M phase boundary showing a large piezoelectric response d15 which reached 1.64 × 105 pm/V. In comparison, the c-PE and M-aa phase boundaries exhibit a superior dielectric constant ε33 over 1 × 105 around um = 0.316% and the piezoelectric response d33 reached 7235 pm/V. The large electrocaloric responses appear near the paraelectric- ferroelectric phase boundary. These insights offer a guidance for experiments in epitaxial PIN–PMN–PT thin films.

• Hydride-enhanced strain localization in Zr alloys is studied using the CPFEM. • Simulated features of slip-hydride interaction match experimental observations. • Slip-hydride interaction depends on orientation relation between slip and hydride. • Mechanisms of strain localization in hydrogenated Zr alloys are revealed. • The influences of misfit strain on strain localization should not be neglected. Hydride precipitation in zirconium (Zr) alloys leads to the deterioration of mechanical properties in key components of nuclear reactors. However, the underlying mechanisms governing the failure initiation of hydrogenated Zr alloys remain incompletely understood. This study focuses on investigating the effects of δ-phase hydride precipitation on the local deformation behavior of Zr alloys. A crystal plasticity finite element method is used to simulate micropillar compression tests of single-crystal samples and macroscale tensile tests of polycrystalline samples. Our results reveal that in the case of micropillar B containing δ-hydride (where the hydride is oriented at 45° from the loading direction), the shear along the hydride–matrix interface and the misfit strain induced by hydride precipitation synergistically contribute to strain localization of Zr alloys. However, for micropillar P containing δ-hydride (where the hydride is parallel to the loading direction), the introduction of hydrides does not enhance the strain localization. Instead, it impedes the local prismatic slip. On the other hand, examination of polycrystalline samples through simulations indicates that hydrides enhance the strain localization of Zr alloys. This effect arises from several mechanisms: shear stress along hybrid–matrix interface, promoting plastic slip in the direction close to this interface; hydride-induced hindrance to certain slip bands, leading to non-uniform local deformation; and misfit strains induced by hydride precipitation, contributing to localized deformation around the hydrides. [Display omitted] [ABSTRACT FROM AUTHOR]

The electrocaloric (EC) effect in dielectrics has shown great potential in the next-generation solid-state refrigeration; however, most dielectrics cannot satisfy the requirement for refrigeration at various temperatures. How to control large EC response to various temperatures is a critical problem for practical cooling applications. In this work, based on entropy analysis, a nonlinear thermodynamic approach considering mechanical loading has been generalized to demonstrate mechanical control of EC response in epitaxial ferroelectric Ba x Sr 1− x TiO 3 (BST) thin films. The effects of chemical composition x , in-plane misfit strain u m , and out-of-plane external uniaxial stress σ 3 on the phase diagrams, phase transition temperatures, and EC response of BST thin films have been studied. The results reveal that a large EC temperature change Δ T appears in the vicinity of c -PE and r-aa phase boundaries, because the polarization component P 3 becomes zero across both phase boundaries, leading to a large change of order in dipoles. It is found that the phase structures and the transition temperatures are sensitive to misfit strain and stress. Large EC response in BST thin films can be controlled and shifted to various temperatures over a wide temperature range for practical applications. It also indicates that the peak of Δ T can be shifted to higher temperature under in-plane compressive strain u m , while it is shifted to lower temperature under tensile strain u m or compressive stress σ 3. Furthermore, the optimal combination of misfit strain and stress for the EC temperature change are identified, which further enhances EC response. These insights offer an alternative pathway to control and implement EC refrigeration over a wide range of temperature. [ABSTRACT FROM AUTHOR]

In the present work, the effect of a pre-existing nanovoid on martensitic phase transformation (PT) is investigated using the phase field approach. The nanovoid is created as a solution of the coupled Cahn–Hilliard and elasticity equations. The coupled Ginzburg–Landau and elasticity equations are solved to capture the martensitic nanostructure. The above systems of equations are solved using the finite element method and COMSOL code. The austenite (A)–martensite (M) interface propagation is investigated without the nanovoid and with it for different nanovoid misfit strains and different temperatures. With the nanovoid, the evolution of the moving interface is changed even before it reaches the nanovoid surface due to the nanovoid stress concentration. It is also found that for small misfit strains, pre-transformation occurs near the nanovoid. For larger misfit strains, martensite nucleates and grows near the nanovoid surface and coalesces with the moving interface. The nanovoid shows a promotive effect on the PT with an increase in the rate of transformation, which is discussed based on the transformation work distribution. The effect of the nanovoid is more pronounced on a curved interface. The nanovoid-induced martensitic growth is mainly dependent on the transformation strain tensor. Examples for different transformation strains are presented where a stable non-complete transformed sample with no void becomes unstable in the presence of the nanovoid. The presented model and results will help to develop an interaction model between nanovoids and multiphase structures at the nanoscale. [ABSTRACT FROM AUTHOR]

Even though it is widely accepted that the Laves phase is a promising strengthener for chromium-containing stainless steels, there is little information available on its microstructural evolution and growth. Therefore, in this study, we analysed the behaviour of Laves (C14) precipitates in high-Cr ferritic stainless steel, Fe-20Cr-2Mo-0.5Nb (at%), annealed at 1073 K for different time periods. A high density of (Fe,Cr) 2 (Mo,Nb) precipitates was formed in the α matrix during annealing. Morphological evolution in the Laves phase followed the sequence of spheroidal → faceted ellipsoidal → faceted needle-like → faceted plate-like. The Laves phase is related to the α matrix by two sets of orientation relationships, viz. OR-1: [ 1 ¯ 1 ¯ 2 ] α / [ 1 2 ¯ 10 ] L , [ 111 ] α / [ 0 1 ¯ 10 ] L , and (1 ¯ 10) α / (000 1 ¯) L and OR-2: [ 1 1 ¯ 0 ] α / [ 0001 ] L , [ 113 ] α / [ 1 ¯ 1 ¯ 20 ] L , and (3 ¯ 3 ¯ 2) α / (1 1 ¯ 00) L. The habit plane of the Laves phase was found to deviate slightly from the (3 ¯ 3 ¯ 2) α / (1 1 ¯ 00) L plane. Interfacial defects, namely disconnections ( b D, h) and super disconnections (m b D , mh), observed experimentally along the habit plane, were consistent with theoretical results based on OR-2 as the reference coordinate frame. The Burgers vector b D exhibited an edge component b y D (0.1539 nm) parallel to Y / [ 113 ] α / [ 1 ¯ 1 ¯ 20 ] L and a small normal component b z D (0.0747 nm) perpendicular to the terraces; meanwhile, the overlap step height h = d (1 1 ¯ 00) L. The morphological evolution of Laves precipitates was described based on the lateral motion of disconnections and super disconnections on { 3 ¯ 3 ¯ 2 } α / { 1 1 ¯ 00 } L terraces in the 〈 113 〉 α / 〈 1 ¯ 1 ¯ 20 〉 direction. Arrays of the disconnections ( b D, h) were found to be capable of accommodating the misfit strain on { 3 ¯ 3 ¯ 2 } α / { 1 1 ¯ 00 } L terraces. Image, graphical abstract [ABSTRACT FROM AUTHOR]

It is shown that very large stresses may be present in the thin films that comprise integrated circuits and magnetic disks and that these stresses can cause deformation and fracture of the material. For a crystalline film on a non-deformable substrate, a key problem involves the movement of dislocations in the thin film. An analysis of this problem provides insight into both the formation of misfit dislocations in epitaxial thin films and the high strengths of thin metal films on substrates. We develop in this paper, theoretical calculations for dislocation nucleation phenomena in nanomaterials obtained by hetero-epitaxial growth of thin films on substrates having lattice mismatch defects. Atomic force microscopy observations showed the nucleation of dislocations from free lateral surfaces to relax the "misfit" strain, here we explain the principle of nucleating edge dislocations from these surfaces by the theoretical calculation, using the method of image stress and energy study. We begin, by treating the case of a single dislocation and then generalize the work at a pile-up of n interface dislocations.

Pulsed laser deposition is widely used to grow BaTiO3 thin films. We investigated the influence of oxygen pressure during growth on the topography, microstructure, and roughness of ferroelectric epitaxial BaTiO3 thin films. It also presented an analysis of the epitaxial growth mode and defects throughout the film thickness using aberration-corrected transmission electron microscopy. Although ferroelastic (twin boundary) domain walls are absent, several misfit dislocations were observed and might be the primary cause of the observed island growth mode. [ABSTRACT FROM AUTHOR]

Ferroelectric flux-closure domains have attracted great attention due to their potentials in high density data storage. For their future applications, it is important to understand their evolution with different factors, such as misfit strain. In this work, a flux-closure domain consisting of a vertical 180° domain wall with two symmetric a domains in both ends ("I" type closure) was observed in nearly unstrained SrTiO 3 /PbTiO 3 multilayers by aberration corrected Transmission Electron Microscopy, which was speculated to be mainly induced by the strong depolarization field near the interface. With the tensile strain increasing, the small a domains in "I" type flux-closures grow gradually and eventually change to the well-known "V" type flux-closures. On the basis of a combination of experimental results and phase field simulations, the phase diagram of the stabilized domain arrays versus the strains in PbTiO 3 films are established. These results provide significant information on understanding the formation mechanism of flux-closure domains and shed light on their controlled growth. In addition, it paves a way to reduce the economic cost in their commercial applications because the SrTiO 3 substrate is easy to synthesize and much cheaper than scandate substrates. Image 1 [ABSTRACT FROM AUTHOR]

Abstract The excellent combination of high strength and high ductility of drawn pearlitic steels is likely derived from the synergistic effects between the ferrite and cementite phases. However, the detailed mechanism, especially the mechanism responsible for the improvement in ductility, has not yet been fully elucidated. In this study, to achieve improved ductility of drawn pearlitic steels, interfacial-dislocation-controlled deformation and fracture in nanolayered composites of ferrite and cementite phases with the Bagaryatsky relationship are investigated via uniaxial tensile and compressive deformation tests using molecular dynamics simulations. Various modes of inelastic deformation are observed at the yield point according to the spacing of interfacial dislocations on the interface between the ferrite and cementite phases in the nanolayered-composite models. Spacing of the interfacial dislocations, which accommodates misfit strains between the ferrite and cementite phases, determines the phase stress and the interfacial dislocation structure in the nanolayered-composite models. This phase stress and interfacial dislocation structure influences the resolved shear/normal stress and the critical resolved shear/normal stress for each inelastic-deformation mode, respectively. Thus, interfacial dislocation spacings can control which inelastic deformation mode is activated at the yield point. We find specific interfacial dislocation structures on the ferrite–cementite interface that nucleate lattice dislocations with lower Schmid factors at the first plastic event. This interfacial dislocation structure can improve the ductility of drawn pearlitic steels because the high strain-hardening rate in the ferrite phases, resulting from the nucleation of dislocations with lower Schmid factors, is clearly expected to suppress the concentration of plastic deformation in the cementite phase [T. Ohashi et al., Mater. Sci. Eng. A 588 (2013) 214–220]. The possibility of the interfacial-dislocation-controlled deformation and fracture enabling higher ductility of drawn pearlitic steels is discussed. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Widmanstätten Ferrite (WF) formation is a complex transformation process, in which various physical variables are involved. In this work, we propose a phase field model of WF formation, which involves the interfacial anisotropy, misfit strain and multicomponent diffusion, for comprehending their coupled effects. The Fe-N-C system is adopted in numerical simulation and the realistic thermodynamic parameters are used. Attention is paid to growth speed and radius of the WF tip, which are dependent on the strength of anisotropic interfacial energy, eigenstrain, concentration and temperature. The simulation results reveal the individual effect of each of these variables and that none of the separate effect can be strong enough to achieve the large aspect ratio of Widmanstätten pattern. The morphology should be the result of their combined effect, which is not a simple linear super-position. Highlights • Phase field model for Widmanstätten formation in steel is proposed. • Interfacial anisotropy, misfit strain and multicomponent are considered. • Widmanstätten tip velocity and curvature are investigated. [ABSTRACT FROM AUTHOR]

From the perspectives of scientific researches and practical applications, it is desirable to explore high operating temperature ferromagnetic films. The effect of biaxial strain on magnetic properties of (110)-oriented La 0.7 Sr 0.3 MnO 3 films was studied. High quality La 0.7 Sr 0.3 MnO 3 films were grown on (110)-oriented perovskite single crystal substrates using pulsed laser deposition, varying substrate-induced misfit strains from − 2.27–0.75%. A remarkable enhancement of Curie temperature has been achieved for (110)-oriented La 0.7 Sr 0.3 MnO 3 films clamped with small misfit strains (i.e., grown on LAST (110)). The enhanced Curie temperature of (110)-oriented La 0.7 Sr 0.3 MnO 3 films could be attributed to the misfit strain between the films and the underlying substrates and may have technological implication for applications at high temperature environments. [ABSTRACT FROM AUTHOR]

The introduction of a dislocation from one lateral surface of a two-dimensional buried layer embedded in a matrix has been theoretically investigated in the interfaces between the two materials. It is found that the lower (and longer) interface is a preferential site where the dislocation can be introduced to relieve the misfit strain. For given layer thickness and lattice mismatch between the matrix and the layer phases, a critical angle has been determined beyond which the introduction of the dislocation is energetically favorable. A stability diagram associated with the dislocation formation has been then provided with respect to the misfit strain, inclination angle and layer thickness. The case of a Si x Ge 1 − x layer embedded in a Ge matrix is finally discussed. [ABSTRACT FROM AUTHOR]

In this work, the eXtended finite element method (XFEM) is implemented for the multiphysics analysis of edge dislocations near a heterostructure (bi-material) interface with nonuniform misfit strain. A novel enrichment is defined to incorporate the singular behavior of the electric potential due to dislocation. Nonlinear material properties due to temperature are taken for a thermo-electro-elastic analysis. The constituting materials having different lattice parameters result in a mismatch–misfit​ strain near the interface. This nonuniform misfit strain distribution affects the dislocations near the bi-material interface. Volterra dislocation modeling is performed to obtain all the primary and secondary fields around dislocations. An expression of the Peach–Koehler force considering the combined effect of the multiple fields is proposed. The results are obtained when the misfit strain is present on one side of the interface and both sides of the interface. A comparative study is performed on the Peach–Koehler force obtained in different cases of the misfit consideration with the case when the misfit strain is absent. Also for the case when the misfit strain is taken on the same side of the interface, the Peach–Koehler force is obtained by varying the misfit percentages corresponding to the different amounts of misfit relaxation. [ABSTRACT FROM AUTHOR]

In functional oxide films, different electrical/mechanical boundaries near film surfaces induce rich phase diagrams and exotic phenomena. In this paper, we review some key points which underpin structure, phase transition and related properties in BiFeO3 ultrathin films. Compared with the bulk counterparts, we survey the recent results of epitaxial BiFeO3 ultrathin films to illustrate how the atomic structure and phase are markedly influenced by the interface between the film and the substrate, and to emphasize the roles of misfit strain and depolarization field on determining the domain patterns, phase transformation and associated physical properties of BiFeO3 ultrathin films, such as polarization, piezoelectricity, and magnetism. One of the obvious consequences of the misfit strain on BiFeO3 ultrathin films is the emergence of a sequence of phase transition from tetragonal to mixed tetragonal & rhombohedral, the rhombohedral, mixed rhombohedral & orthorhombic, and finally orthorhombic phases. Other striking features of this system are the stable domain patterns and the crossover of 71° and 109° domains with different electrical boundary conditions on the film surface, which can be controlled and manipulated through the depolarization field. The external field-sensitive enhancements of properties for BiFeO3 ultrathin films, including the polarization, magnetism and morphotropic phase boundary-relevant piezoelectric response, offer us deeper insights into the investigations of the emergent properties and phenomena of epitaxial ultrathin films under various mechanical/electrical constraints. Finally, we briefly summarize the recent progress and list open questions for future study on BiFeO3 ultrathin films.

Under intense heating and/or deformation, pure nanocrystalline (NC) metals exhibit significant grain coarsening, thus preventing the study of length scale effects on their physical response under such conditions. Hence, in this study, we use in-situ TEM heating experiments, atomistic modeling along with elevated temperature compression tests on a thermally stabilized nanostructured Cu–10 at.% Ta alloy to assess the microstructural manifestations caused by changes in temperature. Results reveal the thermal stability attained in NC Cu-10 at.% Ta diverges from those observed for conventional coarse-grained metals and other NC metals. Macroscopically, the microstructure, such as Cu grain and Ta based cluster size resists evolving with temperature. However, local structural changes at the interface between the Ta based clusters and the Cu matrix have a profound effect on thermo-mechanical properties. The lattice misfit between the Ta clusters and the matrix tends to decrease at high temperatures, promoting better coherency. In other words, the misfit strain was found to decrease monotonically from 12.9% to 4.0% with increase in temperature, leading to a significant change in flow stress, despite which (strength) remains greater than all known NC metals. Overall, the evolution of such fine structures is critical for developing NC alloys with exceptional thermo-mechanical properties. [ABSTRACT FROM AUTHOR]