Effect Of Crystallographic Texture Research Articles

Effect of crystallographic texture on precipitation induced anisotropy in an aluminium magnesium silicon alloy

Abstract The effect of crystallographic texture on precipitation induced anisotropy in yield strength of an aluminium magnesium silicon alloy was investigated. Solutionized samples were subjected to unidirectional and multi-step cross rolling to yield distinct crystallographic textures in the Al–Mg–Si alloy. The rolled sheets were then subjected to annealing followed by second solutionizing treatment to provide sheets with similar grain size and dislocation content but distinct texture. Ageing experiments were carried out on these sheets at 443 K for different time intervals. It was observed that the evolution of anisotropy in yield strength of the age hardened alloy depends on texture. The difference in age hardening response brought about by varying initial texture controls the evolution of anisotropy in mechanical properties of the alloy. This was manifested in terms of transition from anisotropic to isotropic mechanical properties in the unidirectionally rolled samples after peak ageing. On the contrary, a transition from isotropic to anisotropic yield behaviour was observed for multi-step cross rolled samples. This is attributed to enhanced precipitation hardening in crystallographically softer orientations compared to crystallographically harder orientations.

Mapping the magnetic and crystal structure in cobalt nanowires.

Using off-axis electron holography under Lorentz microscopy conditions to experimentally determine the magnetization distribution in individual cobalt (Co) nanowires, and scanning precession-electron diffraction to obtain their crystalline orientation phase map, allowed us to directly visualize with high accuracy the effect of crystallographic texture on the magnetization of nanowires. The influence of grain boundaries and disorientations on the magnetic structure is correlated on the basis of micromagnetic analysis in order to establish the detailed relationship between magnetic and crystalline structure. This approach demonstrates the applicability of the method employed and provides further understanding on the effect of crystalline structure on magnetic properties at the nanometric scale.

The effects of crystallographic texture and hydrogen on sulfide stress corrosion cracking behavior of a steel using slow strain rate test method

The effects of pre-charged hydrogen inside steel and the hydrogen ions on its surface on the sulfide stress corrosion cracking (SSCC) behavior was studied by slow strain rate tests. The specimen had an ASTM grain size number of about 11. Most of precipitates were 30–50 nm in size, and their distribution density was about 106 mm−2. The crystallographic texture consisted of major α-fiber (〈110〉//RD) components with a maximum peak at {115}〈110〉 relatively close to {001}〈110〉, and minor γ-fiber (〈111〉//ND) components with a peak slightly shifted from {111}〈112〉 to {332}〈113〉. Hydrogen was pre-charged inside the steel by a high-temperature cathodic hydrogen charging (HTCHC) method. SSCC and corrosion tests were carried out in an electrolytic solution (NaCl: CH3COOH: H2O: FeCl2 = 50: 5: 944: 1, pH = 2.7). The corrosion potentials and the corrosion rates of the specimen without hydrogen charging for 24 hours were −490 mVSHE and 1.2 × 10−4 A cm−2, and those with charging were −520 mVSHE and 2.8 × 10−4 A cm−2, respectively. The corrosion resistance in the solution with 1000 ppm iron chloride added was decreased significantly, such that the corrosion potential and corrosion rate were −575 mVSHE and 3.5 × 10−4 A cm−2, respectively. Lower SSCC resistance of the pin-hole pre-notched specimen was observed at the open circuit potential than at the 100 mV cathodically polarized condition. Pre-charged hydrogen inside of the specimen had a greater influence on the SSCC behavior than hydrogen ions on the surface of the specimen during the slow strain rate test.

Preferred orientation of grain boundary plane in recrystallized high purity aluminum

Compared with the research of preferred orientation of crystals (crystallographic texture) which started nearly a century ago, preferred orientation of grain boundary plane in polycrystalline materials is a lately proposed research direction with the development of five parameter analysis which is based on electron backscatter diffraction and stereological method. Systematic investigations into the preferred orientation of grain boundary plane and in-depth understanding on their evolution natures will be important to the manipulation of the microstructures of desired properties. In current paper, high purity aluminum (99.99 wt%) samples were cold rolled with 85% thickness reduction followed by a recrystallization annealing at 330℃ for 15-60 minutes and then the grain boundary plane orientations were studied. The results indicate there indeed exist preferred orientations of grain boundary planes in the recrystallized microstructure and the preferred orientation evolves sequentially from {2 2 3} to {1 1 1} and {1 0 0} planes during grain growth. Further discussion points out the recrystallization of high purity aluminum after cold rolling could be a so-called continuous recrystallization which involves sub-grain coalescence and sub-grain growing, and low angle grain boundary (mis- orientation angles ranging from 2° to 15°) constitutes the main part of the entire grain boundaries in the recrystallized microstructure. During grain growth, the crystallographic texture evolves from {1 1 0}<1 1 2> (Brass) to {0 1 1}<1 0 0> (Goss) and {0 2 3}<1 0 0>co- existed, and low angle grain boundary planes usually orient on the exact position of low energy tilt boundaries due to the effects of crystallographic texture and crystallographic plane energy. This is the reason for the regular evolution of the preferred orientation of grain boundary planes as observed.

Effect of crystallographic texture on mechanical properties in porous magnesium with oriented cylindrical pores

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 {101¯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 ∼30kJkg−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.

Analysis of yield strength anisotropy of pipeline steel based on crystallographic model

In the analytical modelling of yield strength anisotropy, some deviations between calculations and experiments are generally observed. These deviations are assumed to be the result of conventional crystallographic models for calculation not being able to distinguish the volume fraction of plastically deformed grains when materials yield. In this study, a novel physical model based on Schmid’s law and on a crystallographic model was developed to interpret the yield strength anisotropy of pipeline steel by distinguishing the volume fraction of plastically deformed grains. Commercially hot rolled API X100 pipeline steel was used. The proposed model confirms the combined effect of crystallographic texture and volume fraction of plastically deformed grains on the yield strength anisotropy of the X100 pipeline steel. The volume fraction of plastically deformed grains when yielding was found to be related to the orientation factor distribution determined by the crystallographic texture.

Numerical Study on the Influence of Crystallographic Texture and Grain Shape on the Yield Surface of Textured Aluminum Sheet Material

The paper investigates by numerical modeling the effects of crystallographic texture and grain shape on the shape of the yield surface of aluminum sheet material at small strains. Different representative volume elements (RVEs) of the material are considered. Plane stress state is assumed in the sheet. A rate-dependent model of crystal plasticity (CP) is used in combination with either the full-constraint (FC) Taylor model or the finite element method (FEM) to compute the volume averaged stress of the material. The effect of different crystallographic textures observed in aluminum alloys on the shape of the yield surface is firstly investigated. An analytical yield function is used to generate yield surfaces for the different crystallographic textures. The deviation between the stress states at yielding computed by FC-Taylor model and the analytical yield surface is used to evaluate the capability of the yield function to fit the anisotropic yield surfaces representing different strong crystallographic textures. Two different shapes of the grains are introduced in the RVEs of CP-FEM in order to study the effect of the grain morphology. Small effects of grain shape are found at small strain compared with the marked influence of crystallographic texture.

Influence of crystallographic texture and microstructure on elastic modulus of steels

In this paper the effects of crystallographic texture and microstructure on the elastic modulus of different grades of steel have been collected from the available literature and put in one place. It is expected that this will help researchers in their understanding of both the fundamental and the practical aspects of the different grades of steel used for various purposes.Dans cet article, on a recueilli à partir de la littérature disponible et rassemblé en un seul lieu les effets de la texture cristallographique et de la microstructure sur le module l’élasticité de différentes nuances d’acier. On s’attend à ce que cela aide les chercheurs dans leur compréhension tant des aspects fondamentaux que pratiques des différentes nuances d’acier utilisées à diverses fins.

Influence of Microstructure on the Performance of Nitinol: A Computational Analysis

One material that has found particular favor for use in biomedical endovascular stents is the near equi-atomic NiTi alloy, Nitinol. One remarkable trait exhibited by this superelastic material is the improvement of its fatigue performance with increasing mean strain (Ref 1, 2). Clarification into this phenomenon still remains incomplete in the literature. This study proposes a microstructural explanation for this unique macroscopic behavior; it is hypothesized stress-induced martensite (SIM) will stabilize with increasing strain which, in turn, leads to the observed increase in fatigue life. Finite element analysis (FEA) is employed to investigate the behavior of a “v-strut” stent subcomponent under various strain levels. The volume fraction of SIM is analyzed to identify its potential influence on macroscopic response and, ultimately, fatigue behavior. In addition, a computational investigation is performed on the effect of crystallographic texture on macroscopic response. Granular transformational behavior is analyzed using FEA models with realistic and idealized grain structures, specifically evaluating the effect of individual grain orientations on the stress-induced martensite transformation.

Effect of crystallographic texture on the bulk magnetic properties of non-oriented electrical steels

Quantitative physical models for non-oriented electrical steels require precise knowledge of chemical and microstructural parameters for the material, with crystallographic texture being one of the most important. Describing the structure–property relationships in these materials is made difficult in that all of the parameters have an effect on magnetic properties. In the present study, a set of non-oriented electrical steel specimens are examined, where chemistry and grain size are kept similar from sample to sample, but texture is varied. A new texture parameter called Magnetic Texture Factor is introduced which is defined as the ratio of the volume fractions of 〈100〉 direction to 〈111〉 direction along magnetization vector. It was found that this Magnetic Texture Factor was a better parameter for identifying trends of magnetic properties with crystallographic texture than the often used Texture Factor, which is described as the ratio of the volume fractions of {100} planes to {111} planes.

Asymmetric rolling of thin AA-5182 sheets: Modelling and experiments

The fundamental objective of the present work consists of the improvement of the plastic strain ratio (R-values) of AA-5182 aluminium alloy through improving the crystallographic texture by asymmetric rolling (ASR). The ASR process imposes intense shear deformation across the thickness of the sheet samples, leading to shear texture development. Finite element (FE) simulations of the ASR were first performed in order to investigate the impact of process parameters on the onset and growth of shear deformation throughout the thickness of sheet samples. In the present work, polycrystal simulations were also done to predict the texture evolutions and the mechanical response of the sheets deformed by different rolling processes. Afterwards, experimental studies were conducted. Conventional rolling (CR) as well as two types of ASR processes was carried out to reduce the thickness of the sheet samples. After each process, the rolled sheet samples were annealed. The crystallographic textures achieved in CR and ASR processes and annealing were measured. Furthermore, uniaxial tensile tests on the rolled sheets were also carried out in order to consider the effects of crystallographic texture on the macroscopic anisotropy. In agreement with the FE predictions, the experimental results showed that the shear strain spreads throughout the thickness of sheet samples during ASR and develops the shear texture. The mechanical behaviour and texture evolution predicted by numerical models are in good agreement with the experimental results. The modified texture leads to an increase of normal anisotropy as well as an increase of absolute value of planar anisotropy.

Effect of crystallographic texture on the cleavage fracture mechanism and effective grain size of ferritic steel

The effect of crystallographic texture on impact transition behavior has been studied in a low-carbon steel. Crystallographic texture was found to influence the general yield temperature through its effect on the plastic constraint factor. The effective grain size depends on the angle between the {001} cleavage planes of the neighbouring crystals, rather than the grain boundary misorientation angle as determined from electron backscattered diffraction analysis considering the angle–axis pair.

A multiscale model for reversible ferroelectric behaviour of polycrystalline ceramics

A multiscale model for the behaviour of ferroelectric polycrystalline materials under electro-mechanical loading is proposed. It is based on an energetic description of the equilibrium at the single crystal scale using a statistical estimate of the ferroelectric domain structure. A self-consistent scheme is then used to establish the behaviour of polycrystalline materials. The approach is anhysteretic but hysteresis effects can be added afterwards so as to obtain butterfly ferroelectric loops. It is applied to a tetragonal Lead Zirconate Titanate (PZT). The model allows the investigation of crystallographic texture effects on the overall behaviour and provides an estimate of internal stresses within the material. By way of an example a 〈100〉 fibre texture is predicted to generate as much as 150% more longitudinal strain and 33% more electric induction at 1MV/m compared to an isotropic polycrystal.

Effect of crystallographic texture, anisotropic elasticity, and thermal expansion on whisker formation in β-Sn thin films

Abstract

Effect of Crystallographic Texture on Anisotropy of Yield Strength in X100 Pipeline Steel

The anisotropy of microstructures and mechanical properties in commercial American Petroleum Institute (API) X100 pipeline steel was systematically investigated by experimental measurements. The experimental results show that anisotropy of yield strength could be observed considerably, which should be attributed to the crystallographic textures due to deformation and transformation of texture components. This is because the effect of the inhomogencity of microstructure in different directions on the mechanical properties could be reasonably neglected based on the experimental investigation of grain size distribution. The effect of crystallographic texture on the anisotropy of yield strength was interpreted theoretically based on the relationship between yield strength and average orientation factor.

Effect of texture on grain growth in an interstitial-free steel sheet

Abstract The effect of crystallographic texture on grain growth was studied in two samples from an interstitial-free steel sheet with two different primary recrystallization textures, one with a pronounced {111} fiber texture and the other with an almost random texture. Upon grain growth annealing, the sample with the random texture showed slow continuous grain growth. In the strongly textured material discontinuous grain growth prevailed at a higher growth rate. The effect of texture on the rate of grain growth is discussed in terms of the motion of the grain boundary triple junctions in the two samples with different distributions of grain-to-grain misorientations. Numerical simulations with a 2D vertex model confirmed the influence of the triple junctions on the development of microstructure and texture observed during grain growth in the two differently textured steel samples.

Effect of crystallographic texture on the anisotropy of Charpy impact behavior in pipeline steel

The current study systematically investigated the anisotropy of fracture behavior in commercial API X100 pipeline steel. The experimental results showed that the temperature for transition from ductile to brittle fracture was significantly different in samples with different orientations, defined as anisotropy of fracture behavior in this paper. The inhomogeneity distribution of microstructure (grain size) and the crystallographic texture were systematically analyzed. The difference in grain size of the samples with different orientations can be reasonably ignored in this study. Therefore, the anisotropy of fracture behavior is attributed to the crystallographic textures in which the deformation and transformation texture components were included. The effect of crystallographic texture on the anisotropy of ductile to brittle fracture transition temperature was theoretically interpreted based on the relationship among yield strength, fracture strength, and their average orientation factor.

A generalized Hosford yield function for weakly-textured sheets of cubic metals

We consider rolled sheets of cubic metals which are macroscopically orthorhombic and microscopically aggregates of tiny crystallites. The preferred orientations of the crystallites create crystallographic texture, which is a main cause for the plastic anisotropy of the sheet metal. Crystallographic texture is characterized by the orientation distribution function or, equivalently, the texture coefficients. In this paper we propose, for weakly textured sheets of cubic metals, a new generalization of the Hosford yield criterion, which is applicable for any state of stress and, as a distinguishing feature, incorporates explicitly the effects of crystallographic texture on plastic anisotropy. Besides the principal stresses, our new yield function depends on the principal stress directions, certain texture coefficients (which can be measured by X-ray diffraction or electron backscatter diffraction), and three material parameters, namely the exponent η, the uniaxial yield stress Yiso for the isotropic polycrystal, and a parameter β which describes the strength of the effects of crystallographic texture. We derive formulas with which the three material parameters can be calibrated by uniaxial and/or balanced biaxial tension tests. As examples, the three material parameters are calibrated against (i) the predictions of the Taylor model in uniaxial and balanced biaxial tension tests and (ii) experimental data on directional dependence of the q-value and uniaxial yield stress that pertain to two aluminum alloys. The values of the exponent η determined by calibration with the Taylor model are approximately 10 and 6.6 for FCC and BCC sheet metals, respectively, which square well with the earlier findings of Hosford and coworkers. For the two aluminum alloys studied, it is found that both the plastic anisotropy of the q-value and of the uniaxial yield stress can be described reasonably well by the new yield criterion.

Considerations in fatigue lifing of stress concentrations in textured titanium 6-4

The effect of crystallographic texture has been considered in attempting to derive a total life prediction capability for the titanium alloy Ti6-4. Orientation effects due to texture are shown to be a result of stress relaxation in strain control specimens, and consequently occur in some cases of notched specimens. It is shown that these effects can be predicted using analytical methods such as the Modified Coffin–Manson and Walker strain approaches. Additional failure mechanisms such as cold dwell prohibit accurate predictions at higher R ratios. It is also acknowledged that texture effects can occur in the crack propagation phase of notched specimens and should be considered in a total life model.

Determining the effect of grain size and maximum induction upon coercive field of electrical steels

Although theoretical models have already been proposed, experimental data is still lacking to quantify the influence of grain size upon coercivity of electrical steels. Some authors consider a linear inverse proportionality, while others suggest a square root inverse proportionality. Results also differ with regard to the slope of the reciprocal of grain size–coercive field relation for a given material. This paper discusses two aspects of the problem: the maximum induction used for determining coercive force and the possible effect of lurking variables such as the grain size distribution breadth and crystallographic texture. Electrical steel sheets containing 0.7% Si, 0.3% Al and 24ppm C were cold-rolled and annealed in order to produce different grain sizes (ranging from 20 to 150μm). Coercive field was measured along the rolling direction and found to depend linearly on reciprocal of grain size with a slope of approximately 0.9(A/m)mm at 1.0T induction. A general relation for coercive field as a function of grain size and maximum induction was established, yielding an average absolute error below 4%. Through measurement of B50 and image analysis of micrographs, the effects of crystallographic texture and grain size distribution breadth were qualitatively discussed.