Effect Of Crystallographic Texture Research Articles

Effect of crystallographic texture and grain orientation on tribological properties of WAAM deposited IN625 alloy in weaving deposition strategy

Understanding the variation in the local microstructure and texture of the as-built fabricated by wire arc additive manufacturing (WAAM) is highly challenging. They affect the mechanical and tribological properties of the builds. The deposition patterns and the process parameters are key factors that determine the microstructures and hence other properties. In the present study, builds of Inconel 625 alloy have been manufactured through WAAM by using a weaving pattern. The microstructure and their texture at the different locations of the deposited build have been investigated through electron backscattered diffraction (EBSD) and optical microscopy. The detailed evolution mechanisms of the micro-structure of the build have been studied followed by the quantitative analysis of the grain size, misorientation angles, fraction of recrystallized and deformed grains, and textures. Later the effect of texture components on the hardness, elastic modulus, and coefficient of friction (COF) of the build has been studied by using nano-indetation and nano-scratch tests. The grain size was found to be 33 μm, 110 μm, and 66 μm at the bottom, middle, and top, respectively. The top region was dominated by Cube {001}<uvw>, Goss {011}<100>, and E {111}<110> orientations, which changed to deformed texture Brass {110}<112> and Goss {011}<100> orientations in the middle region and cube texture at the bottom. Hardness was highest at the top region 5.33 GPa, followed by 4.02 GPa in the middle region and 4.74 GPa at the bottom. The COF was highest in the middle region at 0.456, which reduced to 0.323 in the bottom region. Sheared textured grains {111}<uvw> have shown greater value of COF and hardness than the {101}< uvw> and {100}<uvw> texture grains. The study has been carried out to investigate the variation in local mechanical properties due to microstructural variations. It will help industries to design components with homogeneous mechanical properties.

Stress localization investigation of additively manufactured GRCop-42 thin-wall structure

A full-field crystal plasticity (CP) framework is presented for the GRCop-42 alloy to study microscopic mechanical behavior and local stress heterogeneities. The microstructures of additively manufactured (AM) materials are often unique relative to conventionally processed materials, and the local thermal histories drive these differences during the build process. These thermal histories depend on the process parameters (laser power, scan speed, and scan strategy) and the part geometry. Prior research has shown that the mechanical properties of thin-walled structures can vary significantly with wall thickness due to changes in the thermal boundary conditions during manufacturing. It is, therefore, desirable to perform CP simulations based on the phenomenological constitutive model to predict the local mechanical responses induced by microstructural heterogeneities. This work generates representative microstructures based on experimentally collected grain information (i.e., texture) for grain scale stress analysis, and the material constitutive parameters are calibrated using the experimental mechanical testing data. We specifically investigated the effect of crystallographic texture and grain morphologies on the size-dependent mechanical properties of AM GRCop-42. The selection of appropriate material properties for implementing an effective free surface boundary condition and the influence of adjacent buffer layers are also discussed. Analysis of local field results reveals a strong correlation between stress localization and the initial grain orientation. However, no significant relationship between the misorientation of the individual adjacent grains and the average misorientation is observed.

Shape memory and mechanical properties of a Fe-Mn-Si-based shape memory alloy: Effect of crystallographic texture generated during additive manufacturing

The fcc-γ → hcp-ε → bcc-α' martensitic transformation of a Fe-Mn-Si-based shape memory alloy fabricated by laser powder bed fusion (LPBF) is studied for the first time by in-situ neutron diffraction, in-situ high-resolution electron backscatter diffraction and digital image correlation during uniaxial tensile testing. The comparison between horizontal specimens (fabricated with no inclination on the build platform) and vertical specimens (fabricated with 90° inclination on the build platform) shows that sample orientation affects the deformation and transformation behavior of the material, considerably influencing alloy's shape memory and mechanical properties. The reason for the variation in the alloy's behavior is found in the distinct crystallographic texture generated during the LPBF process. In the vertical samples, the preferential 〈110〉 orientation of grains along the loading direction facilitates the martensitic transformation, resulting in enhanced shape memory properties and pronounced work hardening.

Modeling the statistical distribution of fatigue crack formation lifetime in large volumes of polycrystalline microstructures

Microstructure-scale interactions involving crystallographic texture (orientation and disorientation distributions), distributions of grain shape and size, nearest neighbor grains/phases, etc. in polycrystals can be simulated using the Crystal Plasticity Finite Element Method (CPFEM). Digital statistical volume element (SVE) instantiations that comprise a significant number of grains are analyzed by CPFEM to compute fatigue indicator parameters (FIPs) which are used as surrogate measures of the driving force for fatigue crack formation within the first grain or nucleant phase. The computed maximum FIPs usually increase in magnitude with larger numbers of realistic microstructure instantiations or SVEs analyzed. This work predicts the extreme value distribution (EVD) of the maximum FIPs associated with large engineering components comprised of up to 108 SVEs using a recently developed upscaling scheme, based on statistical information identified from simulations involving only hundreds of SVEs, with each SVE containing nominally 264 grains. This scheme is numerically validated by extensive simulations for samples of duplex Ti-6Al-4V microstructure models with sharp transverse texture strained in two characteristic directions. The size of the training dataset for a reliable prediction is determined for different textures and loading directions based on uncertainty analysis. Finally, the statistical distribution of fatigue crack formation lifetime (FCFL) is correlated with the EVD of the maximum FIPs, facilitating quantitative exploration of the effect of crystallographic texture and sample size on the FCFL.

Phase-field study of crystallographic texturing in piezoelectric polycrystals

Crystallographic texturing enables the design of piezoelectric polycrystals that outperform traditional random polycrystals by exhibiting outstanding piezoelectric properties. In this work, phase-field modeling and computer simulation were employed to study the effect of crystallographic texture on the piezoelectric properties of ferroelectric polycrystals at the domain level. Domain evolutions for single crystal, random polycrystal, and textured polycrystal are systematically simulated. The simulations reveal that the [001]-textured polycrystal can fully exploit the intrinsic anisotropic properties of piezoelectric materials by exhibiting a piezoelectric coefficient that is as large as that of single crystal while being much larger than that of random polycrystal. To better understand the mechanism of piezoelectricity enhancement by crystallographic texturing, a theoretical analysis based on Landau theory is provided. In comparison with random polycrystal, the textured polycrystal manifests a flatter energy landscape and thus possesses a higher piezoelectric coefficient.

Effects of Crystallographic Texture on Subsurface Fatigue Crack Generation in Ti–Fe–O Alloy at Low Temperature

Effects of Crystallographic Texture on Subsurface Fatigue Crack Generation in Ti–Fe–O Alloy at Low Temperature

Effect of crystallographic texture and twinning on the corrosion behavior of Mg alloys: A review

Magnesium and its alloys have gained significant popularity due to their light weight and their potential for use as bioresorbable materials. However, their application is limited in practice due to their relatively poor corrosion resistance. Several methods are available for improving the corrosion resistance of Mg alloys for bio-applications such as using different coatings, alloying, and modifying the microstructural parameters such as the grain size and the crystallographic texture. This review provides a comprehensive summary of the effects of crystallographic texture and twinning, as one of the most important deformation mechanisms of Mg and Mg alloys, on the corrosion behavior. Regarding the crystallographic texture, it is shown that theoretically the basal planes should exhibit a lower corrosion rate but in some cases, such as when there is a galvanic effect or when corrosion films control the overall corrosion behavior, different results may take place. Also, there are contradictory results concerning the effect of twinning on the corrosion behavior. Thus, in some cases twinning may provide preferential sites for corrosion due to the higher energies of atoms located in the twin region by comparison with normal atomic positions in the crystalline lattice whereas there are also other examples where experiments show that twins produce more protective films than in the surrounding matrix.

The role of texture on superelasticity and elastocaloric effect in severely rolled Ti-44Ni-5Cu-1Al (at%) shape memory alloy

The effects of crystallographic texture on the superelasticity and elastocaloric effect of nanograin Ti-44Ni-5Cu-1Al rolled sheet are investigated. Stress-strain curves with different orientation angles between tensile direction and rolling direction show that the tensile strain of the sheet is largest in rolling direction (RD) along <110> and smallest in transverse direction (TD) parallel to <100>. This texture dependence is further studied by analyzing the evolution of each strain component. With the increase of the orientation angle, intergranular constraint effect reaches the maximum in TD. As a result, transformation strain and adiabatic temperature change have a similar monotonic decreasing trend. The material coefficient of performance of the sheet reaches 11.2 in RD. This value makes it possible for severely rolled Ti-44Ni-5Cu-1Al sheet to be a potential candidate for solid-state refrigeration application at room temperature.

Charpy impact anisotropy and the associated mechanisms in a hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy plate

The Charpy impact absorbed energy of a hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy plate with different sampling and notching directions was investigated. Strong anisotropic variations occurred in impact absorption energies due to difference of the α phase crystal orientation and microstructural characteristics along different directions. The higher crack propagation energy of the sampling-notching direction sample (RD-ND) resulted in an impact absorption energy of approximately 2.5 times larger than that of the TD-ND, TD-RD and RD-TD samples. Based on the analysis of the α crystal orientation and the TEM microstructure after impact deformation, it was found that the higher absorption energy of the RD-ND sample was attributed to the activities of a large number of {101‾0}⟨12‾10⟩ prismatic slips and the resistance created by grain boundaries against crack propagation, which also resulted in the delamination of the impact fracture surface. Finally, the coupling effect of crystallographic texture and microstructural characteristics on the impact deformation mechanisms of the hot-rolled Ti–6Al–3Nb–2Zr–1Mo alloy was described.

Effect of Crystallographic Texture on the Anisotropic Tensile Behavior of Aluminum Foil and Its Industrial Application

Effect of Crystallographic Texture on the Anisotropic Tensile Behavior of Aluminum Foil and Its Industrial Application

Crystallographic texture- and grain boundary density-independent improvement of corrosion resistance in austenitic 316L stainless steel fabricated via laser powder bed fusion

Improvement of corrosion resistance of austenitic 316L stainless steel via laser powder bed fusion (LPBF) is currently a prominent research topic; however, the effects of crystallographic texture and the related grain boundary density on the corrosion resistance of LPBF-fabricated parts have not been elucidated. For biomedical applications, crystallographic texture control from a single crystalline-like to randomly oriented polycrystalline microstructure is highly attractive for optimizing the mechanical properties (particularly the Young’s modulus) of implants. An investigation of the impacts of crystallographic planes and grain boundaries exposed to the biological environment on corrosion behavior is necessary. 316L stainless steels with different crystallographic textures and grain boundary densities were successfully fabricated via LPBF. The corrosion resistances of the LPBF-fabricated specimens were comprehensively assessed by anodic polarization, dissolution, and crevice corrosion repassivation tests. The LPBF-fabricated specimens showed extremely high pitting potentials in the physiological saline compared with the commercially available counterparts, and importantly, excellent pitting corrosion resistance was observed irrespective of the crystallographic planes and grain boundary density exposed. Moreover, the LPBF-fabricated specimens did not show metastable pitting corrosion even in an accelerated test using an acid solution. The repassivation behavior of the specimens was not affected by LPBF. Such a drastic improvement in the corrosion resistances of the LPBF-fabricated specimens might be attributed to suppression of inclusion coarsening owing to the rapid cooling rate during solidification in LPBF. By using LPBF, the desired crystallographic texture can be introduced based on the desired mechanical properties without concern for corrosiveness. • LPBF dramatically improved localized corrosion resistance of 316L stainless steel. • Corrosion resistance of the LPBF specimens was independent of the exposed plane. • Precipitation and growth of inclusion was suppressed within nanometer-size by LPBF.

Microstructure effects on the machinability behaviour of Ti6Al4V produced by Selective Laser Melting and Electron Beam Melting process

Additive Manufacturing (AM) is gaining widespread attention over the last decade in the areas of product development and prototyping, across aerospace and medical domains. Nevertheless, the built parts are near-net shaped that usually require a machining finish to improve the surface quality and operational life.The current study aims to document the machinability behaviour of the Ti6Al4V parts fabricated by the AM process, which is based on powder bed fusion, namely, Selective Laser Melting (SLM) and Electron Beam Melting (EBM). Further, machinability parameters are correlated with the microstructure and mechanical properties of the material. Face milling operation is performed under finishing conditions to study the response on the cutting forces. The effect of Hot Isostatic Pressing (HIP) and the influence of the build direction on microstructure and machinability have been investigated for the two AM processes. The effect of crystallographic textures and microstructure morphology of α and reconstructed prior β phases on the mechanical properties was studied using shear tests. It was observed that the SLM process primarily produced homogenous and fine α lath structures with less grain boundary α (αGB) grains, leading to low shear resistance and hence generated low cutting forces. On the other hand, the EBM process produced microstructures with variable morphologies, including more grain boundary alpha (αGB) grains and widmenstatten structures which resulted in a higher shear resistance and forces. The results show a striking influence of the microstructure induced by the type of the AM process, build orientation, and the subsequent heat treatment on the shear resistance and their ability to be machined. Further, the crystallographic textures were not strong for both processes and seem not to impact the machining process. The results highlight a strong “process – property” link which demands optimization of the cutting process for the type of the AM process and the resulting microstructure.

Effect of grain orientations on fracture behavior of polycrystalline metals

Currently no systematic approach exists to explicitly quantify the combined effects of anisotropic grain orientations and grain boundary behavior on the fracture of polycrystalline materials. A multiscale cohesive finite element (CFEM) based computational framework is developed to predict the fracture properties such as KIC and JIC of polycrystalline metals as functions of microstructural attributes. The focus is on characterizing the effects of crystallographic texture on fracture toughness. The framework uses computationally generated statistically equivalent microstructure sample sets with varying proportions of textured grains, allowing statistical variations and distributions of the fracture behavior due to microstructural variabilities and the influences of intergranular and transgranular fracture mechanisms to be quantified and analyzed. A crystal plasticity formulation is used to model the anisotropic deformation in the grains. A misorientation-dependent interfacial relation is used to model texture-sensitive crack growth through grains and grain boundaries. The framework allows exploration of the effects of microstructure on the macroscopic fracture measures via the manifestation of the different fracture mechanisms. Calculations carried out for Mo under 2D and a more general 2.5D plane strain conditions capture and delineate the competing effects between (a) intergranular and transgranular fracture and (b) plasticity and crack growth on the overall fracture toughness of the material. Both the 2D and 2.5D models use the same sets of microstructures; the 2.5D model uses columnar grains. The results indicate that, as the fraction of grains with preferred orientation increases, transgranular fracture dominates relative to intergranular fracture. Consequently, the relative contribution of plastic dissipation associated with transgranular fracture is enhanced, resulting in higher overall fracture toughness for the material setting analyzed. The effect is characterized in terms of the effective grain size distribution, fraction of grains with favourably oriented slip systems, and misorientation-dependent GB characteristics. Finally, an analytical correlation is established between the overall fracture resistance and the microstructure attributes.

Impact of grain orientation and phase on Volta potential differences in an additively manufactured titanium alloy.

This work introduces a method for co-localized multi-modal imaging of sub-μm features in an additively manufactured (AM) titanium alloy. Ti-6Al-4V parts manufactured by electron beam melting powder bed fusion were subjected to hot isostatic pressing to seal internal porosity and machined to remove contour–hatch interfaces. Electron microscopy and atomic force microscopy-based techniques (electron backscatter diffraction and scanning Kelvin probe force microscopy) were used to measure and categorize the effects of crystallographic texture, misorientation, and phase content on the relative differences in the Volta potential of α-Ti and β-Ti phases. Given the tunability of additive manufacturing processes, recommendations for texture and phase control are discussed. In particular, our findings indicate that the potential for micro-galvanic corrosion initiation can be regulated in AM Ti-6Al-4V parts by minimizing both the total area of {111} prior-β grains and the number of contact points between {111} β grains and α laths that originate from {001} prior-β grains.

Polycrystal thermo-elasticity revisited: theory and applications

The self-consistent (SC) theory is the most commonly used mean-field homogenization method to estimate the mechanical response behavior of polycrystals based on the knowledge of the properties and orientation distribution of constituent single-crystal grains. The original elastic SC method can be extended to thermo-elasticity by adding a stress-free strain to an elastic constitutive relation that expresses stress as a linear function of strain. With the addition of this independent term, the problem remains linear. Although the thermo-elastic self-consistent (TESC) model has important theoretical implications for the development of self-consistent homogenization of non-linear polycrystals, in this paper, we focus on TESC applications to actual thermo-elastic problems involving non-cubic (i.e. thermally anisotropic) materials. To achieve this aim, we provide a thorough description of the TESC theory, which is followed by illustrative examples involving cooling of polycrystalline non-cubic metals. The TESC model allows studying the effect of crystallographic texture and single-crystal elastic and thermal anisotropy on the effective thermo-elastic response of the aggregate and on the internal stresses that develop at the local level.

The effect of crystallographic texture as a distinct effective parameter on the biocorrosion performance of Ti6Al4V alloy in PBS solution

In this study, different textures of Ti6Al4V alloy at the same microstructure have been developed through heat treatment in the α + β phase region. Scanning electron microscopy and macrotexture analysis were performed on three orthogonal surfaces. The corrosion performance of different surfaces was assessed by open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization in PBS solution. The obtained results showed that the basal texture corrosion rate (3.6 × 10−5 mm/year) was 6 times lower than those of near prismatic texture. SEM investigation of the corroded surfaces showed the formation of a thick crack-free passive layer on the surface having basal texture.

Effects of texture on the functional and structural fatigue of a NiTi shape memory alloy

The effects of crystallographic texture on the fatigue performance of superelastic NiTi sheet were investigated to assess the evolution of plastic deformation and transformation stress (functional fatigue) and the resistance to crack growth (structural fatigue). During uniaxial cycling, about twice as much plasticity accumulated for tensile specimens aligned in the rolling direction (RD) of the NiTi sheet compared to those in the transverse direction (TD). Fatigue experiments on compact tension specimens also showed a 25% lower fatigue threshold and twice the fatigue crack growth rate when loaded in the RD than in the TD. These macroscopic findings correlated with the microscopic observations of crack-tip displacements, where the crack tip opened at a lower stress intensity (K≈0.9 MPam) when loaded in the RD than in the TD (≈1.5 MPam). The dissimilar crack growth rates highlight the strong orientation-dependent mechanisms of plasticity, transformation, and twinning on both functional and structural fatigue. Although the RD had a larger transformation strain that might suggest an enhanced deformation accommodation, under stress-controlled cycling the TD was more resistant to plastic slip, leading to more reversible transformation. Assuming other microstructural aspects are held fixed (composition, grain size, and precipitates), these results suggest that tension along the textures akin to that of the TD (i.e., with a higher density of [100] and lower density of [111] and [110]) is beneficial to fatigue performance during stress-limited cycling.

Influence of Crystallographic Texture on the Corrosion Product Morphology and Corrosion Rate of AZ31 Plate in Simulated Body Fluid

This paper investigates the effect of crystallographic texture on the corrosion product morphology and corrosion behavior of AZ31 magnesium alloy after immersion in simulated body fluid for 3 days. The microstructure and macrotexture analyses are performed through optical microscopy and x-ray diffraction methods, respectively. The polarization test evaluated the corrosion, and the FESEM electron microscope equipped with EDS was used to investigate the morphology of the corrosion products. According to the results, the morphology of calcium phosphate deposit as a corrosion product at the surface with basal texture was a porous cauliflower shape. In contrast, the calcium phosphate deposit at the surface of the nonbasal texture was uniform and nanoworm-like. The corrosion rate at the basal texture surface was higher than the nonbasal one, which is attributed to the difference in the morphology of calcium phosphate film.

Achievements in Micromagnetic Techniques of Steel Plastic Stage Evaluation

Abstract The investigation of plastic deformation and residual stress by non-destructive methods is a subject of large relevance for the industry. In this article, the difference between plastic and elastic deformation is discussed, as well as their effects on magnetic measurements, as hysteresis curve and Magnetic Barkhausen Noise. The residual stress data can be obtained with magnetic measurements and also by the hole drilling method and x-ray diffraction measurements. The residual stress level obtained by these three different methods is different, because these three techniques evaluate the sample in different depths. Effects of crystallographic texture on residual stress are also discussed. The magnetoelastic term should be included in micromagnetic methods for residual stress evaluation. It is discussed how the micromagnetic energy Hamiltonian should be expressed in order to evaluate elastic deformation. Plastic deformation can be accounted in micromagnetic models as a term that increases the coercive field in soft magnetic materials as the steels are.

Effect of Crystallographic Texture on Anisotropy of Mechanical Properties in High Strength Martensitic Steel

The thermomechanical control process (TMCP) is widely applied as one of the effective processes for improving the strength and toughness of steel plates. In actual application, the anisotropies of mechanical properties arising from the crystallographic texture developed during the controlled rolling process are important issues. In this study, the effect of texture on the anisotropies of mechanical properties in an experimentally manufactured YP960 MPa class steel plate was investigated. Strength varied through the plate thickness from the surface to mid-thickness. At the surface, the strength in the longitudinal direction was higher than that in the transverse direction, and in contrast, at mid-thickness, the strength in the transverse direction was higher than that in the longitudinal direction. The major components of the texture at the plate surface were {110}<111> and {112}<111>, whereas those at mid-thickness were {332}<113> and {211}~{311}<011>. It is considered that the texture of the plate surface was formed by shear strain in the austenite region, whereas that at mid-thickness was formed by plane strain compressive. A crystal plasticity analysis based on the initial texture information obtained experimentally revealed that the anisotropies of mechanical properties were strongly affected by the crystallographic orientation.