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A new concept named “rotating magnetocaloric effect (RMCE)” has been proposed and attracted more attention recently. Unlike the traditional MCE that is achieved by moving the magnetic refrigerant in and out of magnetic field, RMCE can be realized by rotating the anisotropic material within the static field, thus implying the possible higher efficiency and simpler device. However, most studies on RMCE are concentrated on single crystals, which are generally more expensive and difficult to prepare in comparison with polycrystals. Therefore, it is highly desirable to search polycrystalline materials with high RMCE. Here, the textured HoNiSi polycrystal is reported to show a giant RMCE, e.g., the rotating magnetic entropy change (−ΔSR) are 18.5 and 26.7 J/kg K and rotating adiabatic temperature change (ΔTR) are 7.0 and 13.4 K under 2 and 5 T, respectively. This giant RMCE over a wide temperature range especially under low field suggests textured HoNiSi as promising material for practical application of rotary magnetic refrigeration. Moreover, the large magnetic anisotropy of HoNiSi is explained by the single-ion magnetic anisotropy theory, and the coherent orientation of crystallographic texture and rare-earth ion moments leads to the large RMCE in the textured HoNiSi polycrystal. This work reveals that the strongly coherent orientation of crystallographic texture and rare-earth ion moments is a key to realize large RMCE in polycrystalline materials.

Mechanically induced migration of grain boundaries and triple junctions not only determines the size and shape of nanostructures created by severe plastic deformation, it substantially affects their mechanical properties as well. Grain growth during deformation of nanostructures has been widely observed. As the nanostructures processed by severe plastic deformation are a consequence of a dynamic equilibrium between refinement and local mechanically induced coarsening, it is widely accepted that such nanostructures would remain stable upon further loading. However, pronounced grain coarsening can be observed when pure UFG copper prepared by high pressure torsion (HPT) is additionally cold rolled. The coarsening continues up to rolling strains, e = 1, i.e. until favourable grain orientations for rolling are developed. For larger strains subsequent refinement to minimum boundary spacing identical to the HPT microstructure is observed. Interestingly, less grain growth is observed for two other sample orientations of the HPT microstructure which are rolled along different directions with respect to the sample coordinate frame. Crystallographic texture of these samples were favourable with respect to the new strain path, highlighting its role for mechanically induced growth and suggesting a distinct influence of grain orientation on the mechanically induced coarsening process.

Lead-free piezoelectric ceramics are urgently needed in the field of electromechanical conversion devices due to the restriction on the use of lead-based ceramics. In this study, the polymorphic phase boundary (PPB) were tuned by incorporating different concentration of (Bi0.5K0.5)HfO3 into the matrix (K0.5Na0.5)(Nb0.965Sb0.035)O3 CaZrO3, and the c crystallographic texture was realized by templated grain growth method. The maximal d33 (∼550 pC/N) and kp (∼72%) were achieved in the c textured ceramics with composition around rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary. It is proposed that the enhanced piezoelectricity should be ascribed to several combined effects, which primarily contain the R-O-T phase boundary facilitating polarization rotation, the crystallographic orientation induced intrinsic piezoelectric anisotropy, electric-field-induced lattice distortion and phase transitions, and NaNbO3 seed-crystal-driven nanodomain structures. This work provides an effective solution to enhance piezoelectric properties by simultaneous tailoring polymorphic phase boundary and using crystallographic texture in potassium-sodium niobate based piezoelectric ceramics. We believe that the simple solution and design principle can also be applied to other piezoelectric ceramic systems, no matter lead-based or lead-free.

Currently, there is significant interest in magnetocaloric materials for solid state refrigeration. In this work, polycrystalline Heusler alloys belonging to the Ni2+xMn1-xGa family, with x between 0.08 and 0.24, were evaluated for the purpose of finding composition(s) with an enhanced magnetocaloric effect (MCE) close to room temperature. Differential scanning calorimetry (DSC) was successfully used to screen alloy composition for simultaneous magnetic and structural phase transformations; this coupling needed for a giant MCE. The alloy with x = 0.16 showed an excellent match of transformation temperatures and exhibited the highest magnetic entropy change, ΔSM, in the as-annealed state. Furthermore, the MCE increased by up to 84 % with a 2 Tesla (T) field change when the samples were thermally cycled through the martensite to austenite transformation temperature while held under a constant mechanical load. The highest ΔSM measured for our x = 0.16 alloy for a 2 T magnetic field change was -18 J/kg-K. Texture measurements suggest that preferential orientation of martensite variants contributed to the enhanced MCE in the stress-assisted thermally cycled state.

The tensile and compressive deformation in porous Mg with unidirectionally oriented cylindrical pores and a unique fiber texture in which the normal direction of the {1 0 1 ¯ 3} plane was preferentially oriented was studied. Porous Mg specimens with unidirectional pores and texture were prepared by unidirectional solidification in a hydrogen atmosphere using a continuous-casting technique and their quasi-static tensile deformation and quasi-static and dynamic compressions were investigated. In tensile loading parallel to the orientation direction of the pores (the “pore direction”), the porous Mg exhibited a large tensile elongation of ∼60% strain despite the presence of ∼42% porosity, whereas it showed high energy absorption of ∼30 kJ kg−1 along the same direction. To clarify these superior mechanical properties, the underlying operative deformation modes and rotation of crystallographic orientation during loadings were analyzed by X-ray pole figures, optical microscopy and crystal plasticity finite-element modeling. The analyses revealed that in the initial stage of both the compression and tensile loadings along the pore direction, basal slip mainly operated. Importantly, the activity of basal slip was enhanced during the tensile loading by rotation of the crystallographic orientation, which resulted in high tensile elongation. On the other hand, the activation of basal slip was initially suppressed by the crystal rotation during compression. However, the localization of basal slip originating from the elongated grains with the unique texture subsequently enhanced the activity of basal slip, which suppressed the steep increase in the flow stress. This unique localized deformation gave rise to the superior impact energy absorption.

The role of both laser pulse length and duty cycle in controlling the grain size and crystallographic texture of diode laser-deposited Waspaloy powder is investigated. Thin-walled test structures of Waspaloy have been produced using a range of pulse parameters and analyzed by means of scanning electron microscopy and electron backscatter diffraction. Results have been correlated with a simple analytical model of the effect of the laser pulse on the substrate temperature and melt-pool geometry in order to help explain the trends observed. Findings show that pulse parameters have a marked effect on the resulting grain morphology and crystallographic orientation. Modelling has indicated that this arises because the microstructure is highly dependent on the melt-pool geometry, particularly the inclination angle of the melt-pool boundary.

A new Taylor-type polycrystalline model has been developed to simulate the evolution of crystallographic texture and the anisotropic stress–strain response during large plastic deformation of high purity α-titanium at room temperature. Crystallographic slip, deformation twinning and slip inside twinned regions were all considered as contributing mechanisms for the plastic strain in the model. This was accomplished by treating the dominant twin systems in a given crystal as independent grains once the total twin volume fraction in that crystal reached a predetermined saturation value. The newly formed grains were allowed to independently undergo further slip and the concomitant lattice rotation, but further twinning was prohibited. New descriptions have been established for slip and twin hardening and the complex coupling between them. Good predictions were obtained for the overall anisotropic stress–strain response and texture evolution in three different monotonic deformation paths on annealed, initially textured samples of high purity α-titanium.

The elastic strain and crystallographic texture of a rhombohedral lead zirconate titanate ceramic have been characterised in the remanent state, after poling, using high-energy synchrotron X-ray diffraction as a function of the grain orientation psi relative to the poling direction. It is observed that the (200) diffraction peak exhibits pronounced shifts as a function of psi, indicating an elastic lattice strain, while others ({111}, {112} and {220}) show marked changes in intensity as a result of preferred ferroelectric domain orientation. It is shown that the (200) peak is not affected by the domain switching itself but rather acts like an elastic macrostrain sensor. A simple Eshelby analysis is used to demonstrate that both the elastic strain and texture vary systematically with psi according to the factor (3cos(2)psi-1). This angular dependence is evaluated through micromechanics modelling. The physical meaning of the texture variations with psi is also discussed. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

About two decades ago, Bunge and Esling [Scripta Metall 1984; 18: 191–5] put forth a novel concept for capturing and simulating crystallographic texture evolution during large plastic strains on metals using an efficient spectral representation of the orientation distribution function. Although this methodology indicated promise, it was never evaluated critically by these authors, possibly because of the high demands it placed on computational resources. In this paper, the Bunge and Esling concept is revisited and evaluated critically for the first time for a range of deformation processes and starting textures. It is demonstrated that this technique is indeed potentially capable of providing good predictions, especially when the higher order terms in the Fourier expansion are included in the analysis.

The feasibility of representing crystallographic textures as quaternion distributions by a series expansion method is demonstrated using hyperspherical harmonics. This approach is refined by exploiting the sample and crystal symmetries to perform the expansion more efficiently. The properties of the quaternion group space encourage a novel presentation of orientation statistics, simpler to interpret than the usual methods of texture representation. The result is a viable alternative to the Euler angle approach to texture standard in the literature today.

The purpose of this experimental study is to investigate the micromechanical fatigue behavior, in terms of slip nature and preferential cracking sites, of a commercial α/β-forged Ti–6Al–4V alloy. Electron backscattering diffraction is extensively used to identify the deformation (prismatic, basal, pyramidal slip) and crack formation modes activated by fatigue at the surface of several hundred primary α nodules. Some fatal crack formation sites are also characterized. Cracking in basal planes is identified as the most critical damage mode leading to fracture. An explanation is proposed which involves the resolved shear stress, taking into account the Schmid factor and the normal stress in relation to the elastic anisotropy of the α-phase. Finally, the spatial distribution of the secondary cracks is analyzed according to the crystallographic textures (macrozones) present on a mesoscopic scale in the Ti–6Al–4V alloy.

A method is presented to determine the misorientation probability distribution function in polycrystalline materials based on a known, analytical or numerical, representation of the associated orientation probability distribution function, i.e., texture. The proposed formulation incorporates the local grain-to-grain orientation correlations by combining local or macroscopic statistical information, and finds a natural interpretation through the well-known stereographic projection (pole-figure) representation. The proposed formulation distinguishes between antiparallel crystallographic orientations, as well as cone-angle and polar angle misorientations. For fiber-textured samples, it is quantitatively shown that highly oriented samples are equivalent to polycrystals with a high density of low-angle misorientations, while completely random (untextured) materials are equivalent to microstructures with a high probability of large-angle misorientations.

Complementary methods were used to analyse residual stresses and texture evolution in Zircaloy-4 sheets which had undergone cold-rolling deformation: X-ray diffraction and the self-consistent model. A modified elastoplastic self-consistent model, adapted to large deformation, was used to simulate the experimental results and showed close agreement with the experimental data. A new formulation of crystal plasticity is proposed. The influence and the role of elastoplastic anisotropy were also studied and explained in this work. Good agreement was found between experimental and predicted crystallographic textures. The contribution and the magnitude of the first- and second-order residual stresses were correctly evaluated using information from the model. Comparison between the X-ray diffraction results and the simulations confirms that prismatic slip is the main active deformation mode in this alloy under large strain.

The orientation texture of pulsed laser deposited hydroxyapatite coatings was studied by X-ray diffraction techniques. Increasing the laser energy density of the KrF excimer laser used in the deposition process from 5 to 7 J/cm(2) increases the tendency for the c-axes of the hydroxyapatite grains to be aligned perpendicular to the substrate. This preferred orientation is most pronounced when the incidence direction of the plume is normal to the substrate. Orientation texture of the hydroxyapatite grains in the coatings is associated with the highly directional and energetic nature of the ablation plume. Anisotropic stresses, transport of hydroxyl groups and dehydroxylation effects during deposition all seem to play important roles in the texture development.

When Ti-6Al-4V is processed by laser powder bed fusion (LPBF), a material with a martensitic microstructure is obtained. Moreover, the presence of internal stresses, an outer surface with relatively high surface roughness and the presence of remnant porosity all influence the fatigue life of high cyclically loaded components. The majority of investigations on LPBF produced Ti-6Al-4V have focussed on a fatigue life method providing valuable, albeit limited, insight into fatigue failure mechanisms. Near-threshold fatigue crack growth rates are vital for describing fatigue crack initiation mechanisms and how these are influenced by residual stress, a martensitic microstructure and build orientation. This study investigates near-threshold fatigue crack growth rates of LPBF produced Ti-6Al-4V. The study makes use of full-size compact tension specimens for fatigue crack growth rate investigations, the contour method for residual stress measurement, and scanning electron microscopy with electron backscatter diffraction to consider both morphological and crystallographic texture. Results show anisotropic near-threshold fatigue crack growth rates that are dependant on residual stress levels and load-ratios. Fracture is predominantly governed by transgranular quasi-cleavage mechanisms, and the fracture path is directed by the columnar prior beta-grain structure resulting in orientation-dependant crack closure effects. Residual stresses result in crack opening that causes a shift of near-threshold fatigue crack growth rates. An intrinsic ΔKth of ~1.6 ± 0.2 MPa√m and critical Kmax of ~ 3 MPa√m is measured that is independent of the stress state but dependant on orientation. It is shown that this anisotropy is linked to morphological texture and to a lesser extent the crystallographic texture of LBPF produced Ti-6Al-4V.

Experimental and computational studies have demonstrated that the structure of grain boundary networks (GBNs), e.g. the connectivity of certain types of grain boundaries (GBs), has a significant impact on macroscopic material properties. Because minor changes in GBN structure can cause large changes in effective properties, it is common to use large microstructures or report averages over many microstructural instantiations with the assumption that results become more representative as the size or number of samples increases. For crystallographic texture, and composite materials, such ideas have been made rigorous through the definition of representative volume elements (RVEs) and statistical volume elements (SVEs). However, for GBNs, the size of an RVE and the cardinality of a set of SVEs have not yet been determined. In this study, we employ stereological methods to evaluate the convergence of triple junction fractions in both idealized and realistic 2D GBNs to quantitatively define RVEs and SVE sets for GBNs. We compare these results to those for crystallographic texture in the same polycrystals and find that the trends for GBNs and texture are remarkably different. Because the vast majority of experimental work currently relies on 2D microstructure characterization, the results obtained for 2D systems have great practical value in and of themselves. However, the stereological approach employed also allows us to make quantitative predictions of RVEs and SVEs for fully 3D microstructures. These results are expected to aid future experimental and computational work in selecting appropriately sized material volumes to achieve robust quantitative results.

Compaction of crystallographic texture data is highly desirable in crystal plasticity simulations because the computational time involved in such calculations scales linearly with the number of crystal orientations. In a recent publication, we have reported a rigorous procedure for reducing large datasets of crystal orientations for cubic-orthotropic and hexagonal-orthotropic polycrystalline metals using symmetrized generalized spherical harmonics (GSH) functions. The procedure relies on a quantitative description of crystallographic texture using an orientation distribution function (ODF) and its series representation using GSH. The core procedure consists of matching the spectral representation of a full-size ODF containing any number of crystal orientations with that of an ODF containing a compact set of orientations. In this paper, we generalize the procedure to any crystal structure with no restrictions to sample symmetry. These major extensions are accompanied by dealing with significantly more dimensions as well as imaginary terms. Two approaches for generating an initial set of orientations in the compact ODF are explored, one based on binning of a given fundamental zone in the Bunge-Euler orientation space and another that takes advantage of MTEX to maximize the compaction. The overall procedure has been successfully applied to compaction of large ODFs for cubic, hexagonal, and orthorhombic polycrystalline metals with orthotropic and no sample symmetry. It is quantitatively demonstrated that texture evolution, twin volume fraction evolution, stress-strain response, and geometrical changes of samples can be accurately simulated to large plastic strains with compact ODFs using crystal plasticity finite element models.

The fabrication of 3-D parts from CAD models by additive manufacturing (AM) is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a fabricated component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) and also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos National Laboratory. The spatial and temporal variations of temperature gradient (G) and growth velocity (R) at the liquid-solid interface of the melt pool were calculated as a function of electron beam parameters. By manipulating the relative number of voxels that lie in the columnar or equiaxed region, the crystallographic texture of the components can be controlled to an extent. The analysis of the parameters provided optimum processing conditions that will result in columnar to equiaxed transition (CET) during the solidification. The results from the numerical simulations were validated by experimental processing and characterization thereby proving the potential of additive manufacturing process to achieve site-specific crystallographic texture control within a fabricated component.

The crystallographic texture and stress state of hydride platelets of two different orientations precipitated in Zr2.5Nb pressure tubes were studied by synchrotron X-ray diffraction experiments using an 80 keV photon beam and an area detector in transmission geometry. Circumferential and radial hydrides with platelet normals along the tube radial and circumferential directions, respectively, were precipitated in tube material loaded up to H contents of 130 wt.ppm. This macroscopic hydride orientation was controlled by application of a load along the tube hoop direction during hydride precipitation. The experiments show that both circumferential and radial platelets are composed of δ-hydrides precipitated in α-Zr grains from a wide range of orientations, but with a clear preference for Zr crystals with their c -axes at an angle of ∼15–20° from the hoop direction. Some moderate differences between the crystallographic texture of the two hydrides result from application of the load during precipitation. The results are explained in terms of an autocatalytic nucleation process and the Zr2.5Nb microstructure. A careful stress analysis revealed that both hydride types are compressed by the matrix on the plane of the platelet, with the largest stresses always found along the axial direction of the tube. Determination of the stress state of the hydride could be exploited as a diffraction signature of the hydride orientation.

Important technological properties of metal sheets, like formability and particularly deep drawability, are strongly affected by the crystallographic texture. The crystallographic orientation of the deformed grains strongly depends on the deformation path applied. The desirable {1 1 1}//ND texture, which is usually related to good deep drawability, cannot be formed in aluminium alloys by conventional rolling and annealing, although it is known to be a shear texture in face-centred cubic metals. Shear deformation in flat product can be imposed by asymmetric rolling (ASR) in which the diameters of working rolls are different, and in this technique could extend the possibilities for texture control of rolled sheet. The potential of the ASR process is modelled by crystallographic texture models and compared with experimental results.

Property closures delineate the complete set of theoretically feasible combinations of macroscale (homogenized) properties in a given material system. A novel spectral framework called microstructure sensitive design (MSD) was recently formulated and demonstrated to be capable of delineating elastic–plastic property closures in a number of composite material systems. In particular, it was successfully applied to cubic polycrystals, where it was assumed that the crystallographic texture had a dominant influence on the macroscale properties of interest. Application of these procedures to hexagonal polycrystals posed significant computational difficulties, because of the need to represent the texture in the hcp polycrystals in a much larger number of dimensions in the Fourier space compared with what was needed for the cubic polycrystals. This paper reports new computational schemes for delineating elastic–plastic closures for hcp polycrystals using the spectral framework of MSD. The primary focus of this paper continues to be on the influence of the crystallographic texture (in the hcp polycrystal) on the components of the macroscale anisotropic elastic stiffness, macroscale anisotropic tensile yield strength, and the macroscale R ratios (ratio of the transverse strains in tensile deformation mode) exhibited by the material.

The recrystallization of a Zr–2Hf alloy sheet deformed by plane strain compression at room temperature and then annealed at selected temperatures has been studied. The evolution of microstructure and crystallographic texture is investigated by in situ high voltage electron microscopy (HVEM), electron back-scattered diffraction (EBSD) and X-ray techniques. The deformed condition shows a heterogeneous microstructure, composed of highly and less deformed zones, and displays a main “tilted” { 0 0 0 1 } 〈 1 0 1 ¯ 0 〉 texture component. The in situ HVEM examinations provide direct experimental evidence of microstructure evolution mechanisms during early stages of recrystallization: (1) rearrangement of dislocation cells into subgrains, (2) formation of nuclei through growth or coalescence of subgrains, (3) growth of nuclei by high angle boundary migration. EBSD and X-ray show that there is little change of the global crystallographic texture during these stages. With increasing annealing temperature or time, the new grains display two texture components, { 0 0 0 1 } 〈 1 0 1 ¯ 0 〉 and { 0 0 0 1 } 〈 1 1 2 ¯ 0 〉 , the first of which disappears during grain growth.

Free-standing line patterns of Cu and Ni were manufactured by applying photo-lithography and subsequent electrodeposition on glass wafers covered with either a polycrystalline Au-layer or an X-ray amorphous Ni-P layer. Several pattern geometries varying in line width, line separation and line length were studied by X-ray diffraction. Quantitative texture analysis revealed that crystallographic texture depends on the type of substrate-layer: while substrate unbiased growth was observed for Cu-lines on amorphous Ni-P, the highly-textured and fine-grained Au-layer strongly favored nucleation of Cu-crystallites of a preferred orientation. For particular pattern geometries, experimental evidence for an epitaxial orientation relation between Cu and Au was found and discussed with respect to various concepts of epitaxial growth. While crystallographic texture of Ni-electrodeposits was independent on the pattern geometry, for Cu-electrodeposits a pronounced pattern dependence of both type and strength of crystallographic texture as well as differences between Cu-lines and non-patterned Cu-films were observed.

Major processes affecting microstructure of a drawn pearlitic wire including lamellae thinning, changes in inter-lamellar interface and metallographic and crystallographic texture, plastic flow localization, and dynamic strain aging were characterized. Heavily drawn pearlite represents a nano-composite with thickness of ferrite and cementite lamellae decreasing during wire drawing. Volume fraction of inter-phase interfaces is comparable with that of pearlitic cementite and they are associated with high elastic stresses. Stretching and rotation of pearlite colonies result in their alignment with the wire axis. This is accompanied by increase in a local ductility at the true strain below from 1.5 to 2 and then decrease at higher strain levels. Development of a strong crystallographic texture causes anisotropy in mechanical properties. Targeted observations of plastic flow at the same region showed two systems of localized shear bands and provided information on their development. A dramatic decrease in elongation to failure in wires after drawing is linked to the existence of the localized shear bands. Dynamic strain aging increases strength and degrades ductility of drawn wires.

A crystal-plasticity-based constitutive model for the large deformation of polycrystalline materials with hexagonal crystal structure deforming by crystallographic slip at high homologous temperatures has been developed. The constitutive model has been implemented in a finite-element program. In our finite-element model of a polycrystal, each element represents one crystal, and a set of crystal orientations which approximate the initial crystallographic texture of the hexagonal material are assigned to the elements. The macroscopic stress–strain responses are calculated as volume averages over the entire aggregate. Nominally homogeneous experiments in simple tension, simple compression, plane-strain compression and thin-walled tubular torsion have been conducted on initially textured commercially pure titanium at 750°C, and the resulting macroscopic stress–strain response and evolution in crystallographic texture have been measured. Numerical experiments were conducted, and matched to the data from the simple tension and compression experiments to determine the operative slip systems and the material parameters in the constitutive model. Using this information, the predictions of the stress–strain response and texture evolution for plane-strain compression and thin-walled tubular torsion are shown to be in good agreement with the corresponding experimental measurements.

The evolution of grain morphology, crystallographic texture, and microhardness in Al bonded to Al 2 O 3 is dealt with. Specimens of a bilayer Al–Al 2 O 3 and symmetric trilayer Al 2 O 3 –Al–Al 2 O 3 were produced by solid-state diffusion bonding. Metallographic examination revealed the size and shape of grains in the Al layer, and the X-ray diffraction technique was used to measure the crystallographic texture at various through-thickness and in-plane locations. The results showed the existence of gradients in grain size, grain shape, texture, and microhardness through the thickness of the Al. Away from the interface, the aluminum grains were equiaxed, with a sharp cube recrystallization texture. Near the interface elongated and slanted grains, with a rotated cube texture, were observed. The microhardness was seen to correlate with the distribution of grain size. Finite element analyses employing crystal plasticity models were carried out to simulate the polygranular flow of Al during diffusion bonding. The interface constraint imposed by the Al 2 O 3 layer was found responsible for the evolution of the observed gradients in microstructure in the Al layer. The predicted grain morphology trend was also in agreement with experimental observations.

The elastic constants of a polycrystalline material are related to the single crystal elastic constants, the distribution of crystalline orientations, and the shapes of the crystallites. In order to address the needs of thin film mechanics, Kneer’s method for obtaining self-consistent polycrystalline elastic constants from single crystal constants is applied to materials with transversely isotropic physical symmetry, cubic, hexagonal, and rhombohedral crystal symmetry, and an average grain aspect ratio. Crystallographic texture contributes more to anisotropy than grain shape in the cubic materials examined. However, grain shape anisotropy is a significant contributor in the hexagonal and rhombohedral crystal symmetries when varying degrees of crystallographic texture exist.

A computer model of the recrystallization process is proposed which incorporates both microstructure and crystallographic texture using a three dimensional lattice. This model is applied to the recrystallization of cold-rolled interstitial free (IF) steel, assuming oriented nucleation at the grain boundaries. The nucleation mechanism is implemented using the concept of subgrain coalescence. This model provides the quantitative information of a change in the volume fraction of the recrystallization, the grain size distribution, and the crystallographic texture.

Superplasticity proceeds from fine-grained structures and requires high intrinsic resistance to grain growth at the deformation temperature. Here, we show that a mixture of two kinds of brittle ordered phases enables superplastic behavior through dynamic recrystallization in an equiatomic medium-entropy VCoNi alloy as a model material. The alloy annealed at 900 °C exhibits a face-centered-cubic single phase. However, in-depth characterization at various length scales reveals that the alloy, when annealed at 800 °C, comprises two ordered phases: κ (Co1.2Ni1.3V) and σ (Co1.5NiV2.5). As a result of the conventional cold-rolling/annealing process and with the aid of an underlying eutectoid reaction, the alloy exhibits a duplex structure with an average grain size of less than 1 μm, i.e. microduplex structure. The size, morphology, and crystallographic orientation do not substantially change during static isothermal holding at 800 °C, which implies a very high resistance to grain growth. With tensile deformation at 800 °C, however, both phases develop into an equiaxed microstructure with low dislocation density and a dramatic change occurs in the crystallographic texture of the κ phase. These variations result from dynamic recrystallization (DRX), which leads to superplastic elongations of 330–450% at 700–800 °C and at strain rates ranging from 10 to 4 to 10−2 s−1. Notably, the superplastic behavior is favorable at the high strain rate due to the enhanced DRX activity, leading to the larger elongation with increasing strain rates. However, deformation-enhanced grain growth occurs concomitantly with dynamic recrystallization; these competitive processes are investigated to elucidate the mechanism of superplasticity in this model material.

The effect of heat-treatment and build orientation on martensitic phase transformation in additively manufactured (AM) 304L stainless steel is studied and compared with conventionally produced wrought material. The relationships between observed martensitic transformations and material microstructures and their effects on mechanical strength are established through experimental observations. In situ high-energy X-ray powder diffraction measurements were performed to monitor the evolution of ϵ and α′ martensite during compressive loading of stainless steel. Electron backscatter diffraction (EBSD) was used to provide insight on initial grain morphology, crystallographic misorientation within grains, and crystallographic texture. Heat treatment alters the microstructure of AM samples creating different initial conditions. This difference in starting microstructure resulted in variability in martensitic transformation during compressive deformation. The rate of martensitic transformation decreased for AM samples treated with temperatures up to 1100∘C, after which the AM microstructures recrystallized, resulting in increased rate of martensitic transformation for those samples treated at higher temperatures. It was also observed that aligning the axis of compression with the AM build direction resulted in a lower rate of strain-induced martensite formation as opposed to aligning the compression axis perpendicular to it. More favorable distribution of crystal orientations in the latter loading orientation promoted martensitic transformation. These and additional experimental observations from EBSD in terms of kernel average misorientation, mean grain orientation spread, and mean crystallite size reveal strong microstructural effects on strength of additively manufactured metallic materials.

Using X-ray diffraction, namely a rocking curve scan, the effect of electrolytic hydrogen charging on the crystal structure in the Fe-36Ni alloy has been studied in comparison with that after gaseous hydrogenation. It is shown that, in contrast to gaseous charging, the electrolytic one induces plastic deformation increasing thereby density of dislocations and causing crystallographic texture. Based on the analysis of available contradictory data on the grain boundary hydrogen diffusion during the measurements of hydrogen permeation and the obtained experimental data, it is proposed that enhanced hydrogen flux along the grain boundaries is due to hydrogen transport by moving dislocations.

A bridgmanite/periclase aggregate is investigated due to its prevalence in the Earth’s lower mantle and its importance for understanding geodynamic processes. In dual-phase polycrystalline aggregates, both strength contrast between phases and single crystal elastic and plastic anisotropy are known to influence the development of intragrain misorientation, and the evolution of crystallographic texture. In this study, full-field crystal plasticity simulations are performed with a finite element solution method, and applied to an aggregate of a mechanically strong orthorhombic phase with perovskite structure (bridgmanite, MgSiO3), and a relatively weaker cubic phase (periclase, MgO). The relative strengths of the phases are parameterized to elucidate the effect that strength contrast has on texture evolution and single-phase simulations are performed for comparison. Overall, results indicate that the relative strength between the two phases influences the development of plasticity, and the overall texture evolution. Results are discussed in light of trends related to the evolution of plasticity and misorientation in the aggregate, and their dependence on both the strength contrast between phases as well as the spatial distribution of grains and phases.

International audience; The scope of this work is to propose a methodology allowing the determination of the single-crystal elasticity constants of a phase included in a multiphase thin film taking into account its microstructure (crystallographic and morphological texture, porosity and multiphase aspect). The methodology is based on the use of a macro-mechanical test, the impulse excitation technique, a micro-mechanical test, X-ray diffraction and the Kröner-Eshelby scale transition model. As a supporting example, it was applied to determine the single-crystal elasticity constants of the Wβ tungsten metastable phase embedded in a two phases (α+β) tungsten thin film deposited on a steel substrate by DC magnetron sputtering. The effects of the grain-shape, the crystallographic texture, the porosity and the Wβ volume fraction on the macroscopic elasticity constants were studied. Among all these effects, it was found that the effect of the Wβ volume fraction was the most pronounced. The effects of the crystallographic and morphological texture on the microscopic elastic behavior of the film were evaluated. No dominance of the crystallographic or morphological texture effect was observed and their contributions depend on the crystallographic plane and the measurement direction.

Assessing the size of representative volume elements (RVEs) for fatigue-related applications is challenging. A RVE relevant to random microstructure requires a volume of material that is sufficiently large to capture the grain/phase heterogeneity that captures all statistical moments of the distribution of the driving force for fatigue crack formation at “hot spot” grains. Consequently, the large size of a microstructure RVE required to study fatigue phenomena is largely computationally intractable and difficult to explore. A more realistic objective in this work is to systematically study, as a function of the size of a statistical sample of microstructure, trends towards convergence of the simulated distribution of driving force for fatigue crack formation. The present work accordingly leverages the recently developed open-source PRISMS-Fatigue framework [Yaghoobi et al., npj Comput. Mater., 7, 38 (2021)] to examine the trends in convergence of extreme value distributions (EVD) of Fatigue Indicator Parameters (FIPs) in progressively larger polycrystalline microstructure realizations of FCC Al alloy 7075-T6 using crystal plasticity finite element method simulations. The results are compared to the traditional method in which ensembles of statistical volume elements (SVEs) are simulated to build up statistics intended to approximate those associated with a larger volume of material. The convergence of EVDs with increase of size of a SVE of microstructure is closely related to the extent of grain nearest neighbor (NN) interactions. Accordingly, the sensitivity of the local micromechanical response at hot spot grains is quantitatively investigated by systematically varying the orientations of NN grains. Results indicate that SVEs with cubic crystallographic texture tend towards convergence of the EVD of FIPs with tens of thousands of grains while the random and rolled textures require larger volumes. Simple relationships based on microstructure parameters (e.g., Schmid Factor, grain size, NN misorientation) do not completely correlate to fatigue hot spot grains. Finally, the sensitivity of the extreme value fatigue response at hot spot grains extends to the 3rd NN when a single neighborhood grain orientation is altered.

is the favoured crystal growth direction during solidification of cubic metals. However, it is the hard magnetisation axis for Ni-rich soft magnetic materials. In this work, a strategy to enhance the magnetic shielding characteristics of laser powder bed processed soft magnetic alloy (permalloy-80) through the control of the crystallographic texture was developed. The strategy involves initially assessing the influence of the process parameters on the development of the (001) orientation within dense builds, then tilting the build orientation to achieve a crystallographic orientation along the magnetisation soft axis. Using this approach, dense cubic samples with the expected (001) texture were produced, with minimised cracking density. Thereafter, cubic samples tilted to achieve (111) and (110) textures were fabricated, as confirmed by X-ray diffraction and electron backscattered diffraction. Over 200 folds improvement in the magnetic susceptibility was found in the (111) textured build, compared with the (100) oriented build. The paper highlights the possibility to control the grain orientations to achieve improved magnetic properties in the build during laser powder bed processing.

A micromechanical study has been conducted on low temperature dwell fatigue resistance in multiphase polycrystalline titanium alloys. The origin of the observed peak in strain rate sensitivity (SRS) over temperature has been explained by the transition from high-stress/low-temperature to low-stress/high-temperature thermally activated dislocation escape. The SRS peak is found to depend considerably on the rate sensitive slip systems in hexagonal close packed (HCP) α phase and body centered cubic (BCC) β phase in Ti alloys. This motivates the study of structural rate dependence, using the SRS peak, in commercially important textured multiphase Ti alloys. It is found that the SRS peak is dependent on texture and phase morphology in multiphase titanium alloys, which is different from some conventional binary alloys. A computational investigation of crystallographic texture shows that stronger rate sensitivity results from polycrystals with higher fractions of grains well-orientated for basal slip activation. This has also been demonstrated in independent experimental studies. Basketweave structures with multiple α variants have been shown to give the lowest SRSs over those with less variant and colony structures. In addition, the SRS peak, for representative textures and morphologies, has been found to be closely related to the creep behaviour in cold dwell fatigue. This understanding is important in microstructural design of titanium alloys for resisting cold dwell fatigue.

Elevated temperatures and large thermal gradients are a significant source of component failure in microelectronics, and are the limiting factor in heat-assisted magnetic recording (HAMR). We have investigated the effect of solid-state dewetting in Au thin films, as a function of local temperature, film thickness, and substrate adhesion. In this work, a localized temperature rise is induced in thin (≤50 nm) polycrystalline Au films on SiO 2 substrates via focused continuous-wave laser irradiation at 488 nm. The magnitude and distribution of the total temperature rise is measured using CCD-based thermoreflectance. This also allows a sensitive measurement of the temperature at which dewetting occurs, showing that for thin Au films without adhesion layers, rapid dewetting can occur at temperatures as low as 50 °C, which corresponds with an absorbed laser power of 4 mW. The time decay of the reflected light from the illuminating laser is used to monitor locally the dynamics of solid state dewetting. TEM diffraction analysis shows significant changes in the microstructure and crystallographic texture of the films as far as 10 μm away from the illuminated area. The use of a thin metallic adhesion layer (such as Ti or Cr) is shown to significantly improve the adhesion of the Au to the substrate, inhibit grain growth, reduce the tendency towards dewetting, and to allow the film to develop a pseudo-biaxial texture.

This study deals with the evolution of strength and microstructure in pure nickel during wire drawing from an initial diameter of 1.74 mm to 30 μm, corresponding to a total true strain of 8.1. Electron backscattering diffraction (EBSD) and X-ray diffraction (XRD) have been used for microstructural characterization. In the later stages of deformation, the fraction of low angle boundaries decreased as did the misorientations within a grain or cell. The dislocation density stabilized at ∼2 × 1015 m−2, and the activation volume decreased from ∼100 b3 at a strain of 1 to ∼ 15 b3 at strains ≳4, where b is the magnitude of the Burgers vector. Cross-sectional EBSD of the wires revealed that a core region had fiber texture, whereas a peripheral shell region had a complex fiber texture due to redundant shear strain. Viscoplastic self-consistent (VPSC) simulations were in good agreement with the crystallographic texture evolution in the wires during drawing. The wire drawing data is compared with other deformation techniques, to provide a broad framework for analyzing microstructure-strength-ductility relationships. At large strains of >2, with an essentially constant dislocation density, the strength can be related solely to Hall-Petch strengthening by a refinement of the transverse grain size.

In addition to design geometry, surface roughness, and solid-state phase transformation, solidification microstructure plays a crucial role in controlling the performance of additively manufactured components. Crystallographic texture, primary dendrite arm spacing (PDAS), and grain size are directly correlated to local solidification conditions. We have developed a new melt-scan strategy for inducing site specific, on-demand control of solidification microstructure. We were able to induce variations in grain size (30 μm–150 μm) and PDAS (4 μm - 10 μm) in Inconel 718 parts produced by the electron beam additive manufacturing system (Arcam ® ). A conventional raster melt-scan resulted in a grain size of about 600 μm. The observed variations in grain size with different melt-scan strategies are rationalized using a numerical thermal and solidification model which accounts for the transient curvature of the melt pool and associated thermal gradients and liquid-solid interface velocities. The refinement in grain size at high cooling rates (>10 4 K/s) is also attributed to the potential heterogeneous nucleation of grains ahead of the epitaxially growing solidification front. The variation in PDAS is rationalized using a coupled numerical-theoretical model as a function of local solidification conditions (thermal gradient and liquid-solid interface velocity) of the melt pool.

TiAl/TiB2 in-situ metal matrix composites (MMCs) with greatly enhanced nanohardness are prepared via selective laser melting (SLM) for the first time in this study. The effect of TiB2 reinforcement on the microstructural characteristics, texture evolution and phase transformation of TiAl-based alloy is investigated. The results show that with increasing the TiB2 content, the average grain size gradually decreases, and the crystallographic orientation transforms from a strong ( 0001 ) direction to ( 10 1 ¯ 1 ) and ( 11 2 ¯ 1 ) directions. Meanwhile, TiB2 has a great effect on the texture of SLM-processed TiAl/TiB2 MMCs. With increasing the TiB2 content, more textured TiAl/TiB2 MMCs can be produced. The TiAl/TiB2 MMCs are dominated by α2 phase and small amounts of γ, B2, TiB2 and TiB phases are also detected. α2 phase contains the most important texture components of prismatic fiber with { 10 1 ¯ 0 } 11 2 ¯ 0> orientation, basal fiber with { 0001 } 11 2 ¯ 0> orientation and pyramidal fiber with { 10 1 ¯ 1 } 11 2 ¯ 0> and { 11 2 ¯ 2 } 11 2 ¯ 3 > orientations. The TiB2 reinforcements are in the forms of the needlelike micro-TiB2 and irregular nano-TiB2 particles in the TiAl-based alloy matrix, and the nano-TiB2 particles are uniformly distributed with the size of 10 nm in length and 3–5 nm in width. The SLM-produced TiAl/TiB2 MMCs exhibit superior nanohardness of 10.57 ± 0.53 GPa, which is much higher than those of the traditional roll bonding fabricated TiB2 reinforced TiAl-based alloy. The findings would be a valuable reference for fabricating TiAl/TiB2 MMCs parts with controlled grain features, crystallographic texture and phase composition, enhanced mechanical properties and complex structures by SLM.

This study explored a novel intermetallic composite design concept based on the principle of lattice strain matching enabled by the collective atomic load transfer. It investigated the hard-soft microscopic deformation behavior of a Ti3Sn/TiNi eutectic hard-soft dual phase composite by means of in situ synchrotron high-energy X-ray diffraction (HE-XRD) during compression. The composite provides a unique micromechanical system with distinctive deformation behaviors and mechanisms from the two components with the soft TiNi matrix deforming in full compliance via martensite variant reorientation and the hard Ti3Sn lamellae deforming predominantly by rigid body rotation producing a crystallographic texture for the TiNi matrix and a preferred alignment for the Ti3Sn lamellae. HE-XRD reveals continued martensite variant reorientation during plastic deformation well beyond the stress plateau of TiNi. The hard and brittle Ti3Sn is also found to produce an exceptionally large elastic strain of 1.95% in the composite. This is attributed to the effect of lattice strain matching between the transformation lattice distortion of the TiNi matrix and the elastic strain of Ti3Sn lamellae. With such unique micromechanic characteristics the composite exhibits high strength and large ductility. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

We have investigated the physical origin of anomalous in-plane thermal expansion (TE) anisotropy leading to invar-like behavior and negative TE in nanostructured NiTi sheets manufactured via severe cold-rolling. The roles of grain size (GS), crystallographic texture, thermally-induced phase transformation, and intrinsic (lattice level) TE of austenite (B2) and martensite (B19′) phases on the macroscopic TE behavior are addressed. It is shown that by controlling the cold-rolling thickness reduction and heat-treatment temperature the coefficient of thermal expansion (CTE) can be controlled in a wide range from positive ( α ∼ 2.1 × 10 −5 K −1 ) to negative ( α ∼ −1.1 × 10 −5 K −1 ) via in-plane anisotropy of TE. A very small CTE of α ∼ −5.3 × 10 −7 K −1 (invar-like behavior) in a wide temperature window of 230 K (353–123 K) is obtained at an angle of 33.5° to the rolling direction (RD) of the severely cold-rolled sheet. TEM and XRD studies show that the microstructure underlying such anomalous TE behavior consists of a mixture of B2 nano-grains and retained/residual deformation-induced martensite and that the observed anomalous TE anisotropy is due to the intrinsic anisotropic TE of residual martensite. The invar-like behavior is the result of the cancellation of the positive TE of austenite phase with the negative TE of residual martensite along 33.5° to the RD. A simple rule of mixture model incorporating the intrinsic TE of B2 and B19′ lattices and the texture coefficients of the sample is proposed which successfully captures the anomalous in-plane TE anisotropy. The discovery of high dimensional stability over a wide temperature window along with temperature insensitive non-hysteretic linear superelasticity of the severely-deformed NiTi opens up a new route for designing stable SMAs for applications in ragged environments.

This study proposes an implementation of the cellular automata finite element (CAFE) model in order to optimize its performance for simulating the solidification of additively manufactured (AM) materials. The translating melt pool in AM leads to a highly localized region of activity at any given time. The time scale associated with the evolving temperature field is much larger than the time scale associated with grain solidification. A separation of temporal scales is proposed such that solidification analysis is treated independently as sub-cycles within each discrete time step of the scanning laser. At each laser time step, all of the domain is idle except a small portion, which is the region where the material is undercooled but has yet to be solidified. This region is identified, and a second partition of the computational resources is established such that the solidification computations are evenly balanced. Numerical studies demonstrate that the proposed implementation achieves dramatic improvement in parallel scalability than previously reported and thus advances the state-of-the-art of CAFE modeling for AM in terms of computational efficiency. This improved computational performance is necessary to simulate the large 3D polycrystalline microstructures required to evaluate texture and grain morphology, and two of such simulations are presented. The model is validated for laser powder bed fusion 316L stainless steel, where the polycrystalline grain morphology and crystallographic texture of the simulated microstructure closely match experimental characterization data. A second simulation is performed for a different scan pattern in order to highlight and evaluate its effect on microstructural features.

We carried out an in situ ultrasonic characterization of a NiTi shape memory alloy polycrystal subjected to pseudoplastic straining. The measurement leads to a full elastic tensor of the transversely isotropic polycrystal during the stress-induced austenite → R-phase → B19 ′ martensite transformation. The results reveal a strong anisotropy of the R-phase already in the low-strain state, which is then retained in character throughout the R-phase → martensite transition and even in the stress-free oriented martensite after the unloading. By using a micromechanical model based on homogenization approaches, we show that this strong anisotropy is probably related to twin boundaries both in the R-phase and in martensite rather than to the anisotropy of the unit cell and the crystallographic texture.

Elastic constants of polycrystalline NiTi and NiTiCu shape memory alloys in the martensite phase were determined by resonant ultrasound spectroscopy; the evolution of these constants was studied with subsequent applications of compressive loads inducing reorientation of martensitic variants. While the initial thermally-induced martensite exhibited only weak elastic anisotropy resulting from the underlying crystallographic texture of the parent phase, the materials with oriented martensitic microstructures exhibited strong elastic anisotropy with Young's moduli in different directions differing by several tens of GPa−s. A qualitative difference in behaviors was observed between the monoclinic B19′ martensite in the NiTi alloy and the orthorhombic B19 martensite in the NiTiCu alloy.

Yield locus measurements and their analytical descriptions has been the bases for modeling metal processing. These analytical descriptions play a role in models to predict limit strains observed during determination of forming limit diagrams of flat metal stock as means to evaluate their fabrication performance. Some of these analytical descriptions use the isotropic or anisotropic plastic potentials that take into account the crystallographic texture of the material. The applicability of such potentials is validated by comparing their predictions to that of unidirectional tensile data. In the current work, this approach is reversed to examine whether the constitutive relations, which replicate the measured stress-strain diagrams, can generate a two-dimensional section of the yield locus. The strategy is to sum the computed plastic work (PW) from unidirectional mechanical tests in two principal directions which also accommodates the biaxial interaction strains. The resulting yield function includes f θ and f φ , the prescribed stress ratios and the texture parameters R φ and R θ in their respective principal directions. The prescribed PW at an arbitrary strain during unidirectional tensile test is equated to the work sum from the biaxial stresses on the premise that the plastic flow-stress registers only the increasing density of obstacles it generates. The computed biaxial yield stresses showed good fits for AA5154 and AA5754 with only small modification due to latent work hardening.

Current approaches to tailoring the thermal expansion coefficient of materials or finding materials with negative thermal expansion rely on careful manipulation of either the material's composition and/or the complex fabrication of composites. Here, by contrast, we report a new principle that enables the precise control of macroscopic thermal expansion response of bulk materials via crystallographic texture manipulation and by taking advantage of anisotropic Coefficients of Thermal Expansion (CTE) in a large class of martensitically transforming materials. Through simple thermo-mechanical processing, it is possible to tailor the thermal expansion response of a single material––without manipulating its composition––over a wide range of positive and negative values. We demonstrate this principle by gradually tuning the macroscopic CTE in a model NiTiPd alloy between a positive (+14.90 × 10−6 K−1) and a negative (−3.06 × 10−6 K−1) value, simply by incrementally increasing tensile plastic deformation in the martensite phase. This surprising response is linked to the large positive, +51.33 × 10−6 K−1, and negative, −34.51 × 10−6 K−1, CTE anisotropy, at the lattice level, along the different crystal directions in martensite. Similar CTE anisotropy is also shown experimentally in CoNiGa and TiNb alloys. In a model TiNb alloy, giant macroscopic CTEs of +181 × 10−6 K−1 and −142 × 10−6 K−1 are measured. A connection between the CTE anisotropy and the martensitic transformation in these and other materials systems such as NiTi, pure uranium, and PbTiO3 is later made. It is shown that negative or positive thermal expansion crystallographic directions are connected to the crystallographic relationship between the austenite and martensite lattices, and can easily be predicted using the lattice parameters of austenite and martensite phases. Our current observations and analyses suggest that the tunability of the macroscopic CTE through thermo-mechanical processing is universal in materials––both ceramic and metals––that undergo martensitic transformations.

The effects of stacking sequence and short-range ordering of solute atoms on the elastic properties of Mg–Zn–Y alloy single crystals with an 18R- or 10H-type long-period stacking ordered (LPSO) structure were studied. Instead of single crystals, the growth of which can be quite difficult, two directionally solidified (DS) Mg–Zn–Y alloy polycrystals, mainly consisting of 18R- or 10H-type LPSO structure, were prepared. X-ray pole figure analyses revealed that fiber textures, which differed in the two prepared alloys, were formed in the DS polycrystals. For the DS polycrystals, a complete set of elastic constants was measured during cooling from 300 to 7.5 or 5.5 K. By analyzing the elastic stiffness of DS polycrystals on the basis of a newly developed inverse Voigt–Reuss–Hill approximation, in which the detailed crystallographic texture could be taken into account, the elastic stiffness components of the single-crystalline LPSO phases from 300 to 7.5 or 5.5 K were determined. The elastic properties of the 18R- and 10H-LPSO phases were also evaluated by first-principles calculations based on density functional theory. Comparison of the measured elastic properties at 5.5 or 7.5 K with the first-principles calculations revealed that the elastic properties of the LPSO phase were virtually dominated by the stacking sequence of the LPSO structures and the formation energy of short-range ordered solute atom clusters, formed at the four consecutive atomic stacking layers. Importantly, the effects of the formation energy and stacking sequence were significant in the elastic moduli related to the atomic bonding between the stacking layers.

This paper presents a comprehensive study of the relationships between deposition conditions, microstructure and mechanical behavior in thin aluminum films commonly used in micro and nano-devices. A particular focus is placed on the effect of porosity, which is present in all thin films deposited by evaporation or sputtering techniques. The influences of the deposition temperature on the grain size, pore size and crystallographic texture were characterized by X-ray diffraction and scanning electron microscopy. The mechanical behavior of the films was investigated using four different methods. Each method is suitable for characterizing different properties and for testing the material at different length scales. Nanoindentation was used to study hardness at the level of individual grains; resonant ultrasound spectroscopy was used to measure the elastic moduli and porosity; and bulge and tensile tests were used to study released films under biaxial and uniaxial tensions. Our results demonstrate that even low porosities may have tremendous effects on the mechanical properties and that different methods allow the capture of different aspects of these effects. Therefore, a combination of several methods is required to obtain a comprehensive understanding of the mechanical behavior of a film. It is also shown that porosity with different pore size leads to very different effects on the mechanical behavior.

The strong thermoelastic–plastic anisotropy of single crystal, orthorhombic α-uranium leads to the generation of significant thermal residual stresses (TRSs) after cooling from the processing temperatures of polycrystals. The present study shows the effect that these TRSs have upon subsequent room temperature deformation after aging. In situ neutron diffraction strain experiments performed on specimens machined from a clock-rolled plate, combined with ex situ texture measurements and elastoplastic self-consistent polycrystalline plasticity modeling, provides the necessary information to quantify the relative strengths and activities of the various deformation mechanisms known to operate within α-uranium. The results demonstrate that the activation of hard slip modes is necessary in order to generate macroscopic flow at the stress levels observed experimentally. Although the thermal residual stresses do not drastically affect the “bulk” response, inclusion of the TRSs drastically improve the agreement between predicted and experimentally measured internal strain evolution and strongly alter the predicted slip and twinning mode activities. As such, modeling efforts to discern the roles of the various mechanisms must account for the presence of thermal residual stress. In agreement with prior crystal plasticity modeling efforts, the crystallographic texture and polarity of twinning mechanisms explain the tension–compression strength asymmetry observed in the material (i.e. significantly more of the soft {1 3 0} twinning mode is observed to occur during compression along the prior plate RD than tension along the same direction).