Crystal Plasticity Analysis Research Articles

Crystal plasticity analysis of tensile plastic behavior and damage mechanisms of additive manufactured TiAl alloy under elevated temperatures

A crystal plasticity model based on Electron Backscatter Diffraction (EBSD) experimental data has been developed to simulate the tensile behavior of additively manufactured TiAl alloys at various temperatures. To accurately capture the activity of different slip systems and their contribution to the material's plasticity, multiple slip systems across different phases are considered. The validity of the model is verified by comparing the simulation results, such as microscopic properties, with experimental and test data. Additionally, a continuous damage model is incorporated to analyze the damage behavior of additively manufactured TiAl alloys at different temperatures. Compared to experimental data, the crystal plasticity model incorporating damage effectively simulates the tensile failure behavior of TiAl alloys across a range of temperatures.

Modeling and Crystal Plasticity Analysis of Strain Hardening in Metallic Materials under the Influence of Microstructure

Modeling and Crystal Plasticity Analysis of Strain Hardening in Metallic Materials under the Influence of Microstructure

Crystal Plasticity Analysis of the Orientation-Dependent Grain Rotation and Fragmentation Behaviors in Ferritic Stainless Steel During Cold Rolling

Crystal Plasticity Analysis of the Orientation-Dependent Grain Rotation and Fragmentation Behaviors in Ferritic Stainless Steel During Cold Rolling

Predicting plastic behavior of magnesium alloy tube bending with comprehensive constitutive models

This paper aims to predict defects occurring in magnesium alloy tube bending through finite element simulations. Deformation tests were conducted to identify and characterize plastic anisotropy, tension-compression asymmetry, and anisotropic hardening behaviors of extruded Mg–Al–Zn-RE alloy rectangular tubes. Limited by size, the deformation tests along the wall thickness of specimens were conducted through crystal plasticity analysis. To thoroughly investigate the material constitutive features affecting bending, two constitutive models, Yoon2014 and Hill48, were established and calibrated. The non-associative flow rule was adopted, and anisotropic hardening was depicted using the yield-surface interpolation method. In comparison, the Yoon2014 model accurately predicted the strain distribution and tube shape collapse of the bent tube with negligible deviation from the experimental data, prior to the Hill48 model. This underscores the necessity of considering comprehensive plasticity models in tube bending simulations.

Crystal plasticity modeling and analysis for the transition from intergranular to transgranular failure in nickel-based alloy Inconel 740H at elevated temperature

The precipitation-strengthened Nickel-based alloy Inconel® 740H® (IN740H) exhibits increased ductility at higher applied strain rates during quasi-static tensile tests at an elevated temperature of 760 °C. The examination of fracture surfaces in this context reveals a noteworthy transition of underlying fracture mechanisms from transgranular to intergranular fracture as the applied strain rate decreases from 1×10−3/s to 0.83×10−4/s. To thoroughly understand the mechanical response of IN740H under these conditions, this study develops a crystal plasticity finite element (CPFE) model. This model incorporates various deformation mechanisms including dislocation slips, climb, and grain boundary sliding, which are relevant to the test conditions. The model is calibrated using data from both tensile tests at different strain rates and creep tests across a broad stress range at 760 °C, enabling the accurate determination of model parameters for each mechanism. Simulation results well captured the experimental observations of different failure modes. At higher strain rates, the model shows a dominance of dislocation slip leading to heterogeneous plastic deformation and formation of transgranular shear bands causing the failure, while at lower strain rates, an increased activity of grain boundary sliding causes grain boundaries crack leading to intergranular failure.

Crystal Plasticity Analyses Around Grain Boundaries Using a Dislocation Dynamics Finite Element Model

We setup a dislocation dynamics finite element framework by bridging a dislocation dynamics program and an open source finite element program. As part of initial verification, deformation of single crystal micro-pillar having single and double glide activation is demonstrated. A case study of a twin boundary is presented wherein the dislocation pile-up at the grain boundary and formation of a residual dislocation are shown. For studying the dislocation interactions with other grain boundaries, model grain boundaries are considered. We consider three synthetic grain boundaries namely transparent, semi-transparent, and impenetrable. The model’s transparent and semi-transparent grain boundaries contain no dislocations and very low density of dislocations in them, respectively, and thus low number of interactions with other dislocations. More junctions and cross-slip occurrences are recorded near the semi-transparent grain boundary. The most dislocation–dislocation interactions near grain boundaries result into glissile junctions. The current results are compared against literature data and it is observed that other than junction formation, cross-slip is very frequency observed near grain boundaries.

Evaluation of fatigue properties in flame-resistant magnesium alloy welded joints by crystal plasticity analysis and data science approach

Evaluation of fatigue properties in flame-resistant magnesium alloy welded joints by crystal plasticity analysis and data science approach

Intra-grain orientation distributions in deformed aluminium: Synchrotron X-ray diffraction experiment and crystal-plasticity finite-element simulation

The development of intra-grain orientation distributions is analyzed for 446 individual grains of an aluminium polycrystal deformed in tension to successive strains of 1, 1.5, 2, 2.5 and 4.5%. In the experiment, diffraction contrast tomography (DCT) and far-field 3D X-ray diffraction microscopy (3DXRD) were used, and a reduced-order representation of the intra-grain orientation distributions was determined from the broadening of the 3DXRD diffraction spots. A high-resolution finite-element simulation (700 elements/grain on average) was conducted on the same polycrystal, providing detailed information on orientation evolution. Several metrics were considered to analyze the experimental and simulated orientation distributions, including the average disorientation angles and the preferential disorientation axes. The average disorientation angles were found to increase almost linearly with strain, and to be in appreciable correlation between experiment and simulation (albeit evolving faster in simulation). It was shown that the preferential disorientation axes are distributed perpendicular to the tensile direction (Z) and perpendicular to the X–Y component of the Rodrigues orientation vector. Detailed crystal plasticity analyses showed that the distribution of preferential disorientation axes is related to the presence of larger slip variabilities on particular slip systems. Using a simplified approach, it was shown that accurate knowledge of the average stress of a grain is necessary in order to predict the preferential disorientation axis, which is well-captured by the finite-element simulation. The intra-grain stress distribution appears to have comparatively less influence.

Crack initiation and propagation dominated by strain localization in quasi-single crystal and poly-crystalline of a Ni-based complex concentrated alloy

Cracking is the precursor of the final fracture for most engineering materials, often affected by various microstructural characteristics including grain orientation, boundary, precipitation, etc. In this study, the fracture behaviour of a typical Ni-based complex concentrated alloy (CCA) was systematically investigated. These CCAs were fabricated using fine-grain casting and directional-solidification processes, which consists of quasi-single crystal (QSC) and poly crystalline structures respectively. Quasi-static tensile test results combined with morphology characterizations and crystal plasticity analyses suggest that microcracks tend to nucleate at the matrix/carbide interfaces in QSC and then propagate along the maximum slip direction at the crack tips. The crack path showed a distinctive zig-zag shape, beneficial for consuming the crack propagation energy. In consideration of carbide morphology, script-typed carbides were found to be very effective in hindering dislocation movements, resulting in admirable work hardening ability. In polycrystalline, however, microcracks are commonly found near the carbides that precipitate at grain boundaries, then developed quickly to connect with each other, leading to premature intergranular fracture. Grain boundary carbides were detrimental to mechanical performance. Considering the large amounts of investigations on second phase and precipitation, these new findings about carbide-related crack behaviours could be extended to other second phase hardening materials, providing new routes to design high-performance alloys by controlling the precipitation morphology and position.

Effect of stress-states on non-classical twinning in three-point bending of magnesium alloys

The influence of stress state on the drivers of non-classical twin nucleation in three-point bending of Magnesium alloy AZ31 is presented in this study. Deformed microstructures and textures at the tensile and, for the first time, shear regions are investigated in detail. The experimental observations coupled with the strain-gradient crystal plasticity analyses show that the shear nucleates more twins compared to the tensile and compressive stress-states at near yield-point. Stored energy density provides mechanistic insight into the local drivers of non-classical twin nucleation observed in the shear stress-state region. Further, the twin variant selection follows the locally stored shear energy density criterion, as opposed to the twin resolved shear stress, indicating that their nucleation is driven by local energy and defect sources.

Complementary research on the Al–Cu nanostructured composite processed by ARB: finite element, crystal plasticity, intermetallic, and failure analysis

A unique Al–Cu composite was manufactured using the accumulative roll bonding (ARB) process. For characterization purposes, a variety of methods was conducted on the resulting composite. Also, the shear band formation which is a prevalent phenomenon in the ARBed materials was analyzed using the finite element method (FEM). For experimental analysis, the crystallographic texture was evaluated for the material by the X-ray diffraction method (XRD). A well-developed rolling (β-fiber) texture was dominated on the Al side, however, recrystallization led to the occurrence of other component mainly around <001> orientation on the Cu side. Upon annealing, the formation of different intermetallic compounds (IMCs) was observed and evaluated using scanning electron microscopy (SEM). An unexpected AlCu4 was detected between the layers as the prominent IMC after the annealing process. Furthermore, the shear punch test was employed for the material's mechanical characterization. It was observed that the strength of the composite material was higher than that of primary metals i.e., Al and Cu. Finally, failure analysis revealed a ductile fracture with separated layers at earlier cycles and a brittle fracture at higher ARB cycles.

Crystal plasticity analysis of fatigue-creep behavior at cooling holes in single crystal Nickel based gas turbine blade components

We build a crystal plasticity finite element framework to investigate slip localisation and fatigue-creep behaviour at the cooling holes of single crystal Nickel (Ni) based components under cyclic thermomechanical loading. The total slip rate is decomposed into a thermally activated dislocation glide rate which dominates at moderate/low temperatures (T) and/or high stresses, and a climb rate which dominates at high temperatures and increases as inelastic strain accumulates. This formulation captures the monotonic and long-term creep response of Ni alloys in the wide range 20 <T < 1100 °C and indicates that room temperature plasticity during unloading increases the high temperature creep rate during loading (creep dwell), eventually increasing the total slip accumulation per cycle; the effect depends on the way the inelastic strain accumulates upon successive slip reversals. Elastic material anisotropy is shown to modify drastically the stress concentration around holes such that slip tends to localise at locations where the max principal stress, tangent to the hole surface, aligns with stiff crystallographic directions. This highlights the importance of plastic and creep anisotropy and creates new avenues for optimising hole shape to minimise slip activity. Our study brings to light key material-component relationships that concern the wider material science, high temperature and fatigue communities.

Three-dimensional crystal plasticity and HR-EBSD analysis of the local stress-strain fields induced during twin propagation and thickening in magnesium alloys

Present work focuses on analysis of the stress and strain fields inside and around the individual {10–12} twin in magnesium alloy. The 3D crystal plasticity model represents twin as an ellipsoidal inclusion surrounded by the matrix. Five different twin thicknesses and three different lateral twin lengths are used for stress/strain analysis. The simulations are complemented with experimental observations using high-resolution electron backscattered diffraction. The simulations and experiments show a similar distribution of the shear stress and the spatial activity of individual slip systems (basal, prismatic, pyramidal). Plasticity induced inside the twin is dominantly caused by the prismatic dislocations slip and does not influence twin back stress which is identical to pure elastic twin. The twin with larger lateral dimension requires lower equilibrium stress which suggests anisotropic twin propagation and increased thickness of such twins. The lateral twin propagation is mostly influenced by prismatic and pyramidal slip in the twin vicinity. The twin thickness can reach a maximal level that is driven by the critical resolved shear stress values for dislocation slip with the significant influence of basal slip.

Influence of Local Microstructural Variations on the Bendability of Aluminum Extrusions: Experiments and Crystal Plasticity Analyses

Abstract The bendability of extruded profiles of an age hardenable aluminum alloy is investigated using mechanical tests on flat tensile specimens and bending specimens. Two profile geometries are considered, where the profiles exhibit different grain structures. The microstructure of the profiles in terms of the crystallographic texture and constituent particles is otherwise comparable. While the tensile properties are not that different for the two profiles, their bendability is strongly dependent on the grain structure and is about twice as high for one profile than for the other. A newly proposed coupled damage and single crystal plasticity model is used in finite element analyses of the mechanical tests to investigate the influence of the grain structure on the bending behavior, and the numerical results are compared to the experimental tests. The crystallographic texture and the grain morphology of the profiles, found by the electron back-scatter diffraction technique, are explicitly represented in the finite element models. The crystal plasticity simulations capture the difference in the bendability of the two profiles, and in agreement with the experiments predict a considerably higher bendability for one of the profiles. It is found that the grain structure affects the shear band formation in these profiles, but also the local texture where the shear bands are located is important for crack initiation and propagation as grains with certain crystallographic orientations may have a higher fracture resistance.

Multi-phase-field and dislocation-based crystal plasticity analysis of martensitic transformation in metastable austenitic steels

Multi-phase-field and dislocation-based crystal plasticity analysis of martensitic transformation in metastable austenitic steels

Crystal plasticity analysis of the evolutions of temperature, stress and dislocation in additively manufactured tungsten

Additive manufacturing (AM) has brought new opportunities for the fabrication of refractory metal tungsten (W). However, the cracking issue in additive manufactured pure W has not been solved, restricting its application. The cracking behavior is associated with the high residual stress, which is caused by the high temperature gradient and cooling rate during AM, as well as the internal brittleness of W. In order to solve this problem, the evolution of the internal microstructure and the corresponding thermal and loading conditions during AM has to be systematically investigated, but the related work is very rare. In the current work, a thermal-mechanical coupled dislocation-based crystal plasticity model is developed, which considers the temperature dependent plasticity induced by the thermal-activated kink-pair mechanism of screw dislocation. This model is applied to investigate the evolution of temperature, stress, and dislocation behaviors in single crystal and polycrystalline W during AM. The influences of crystal orientation and adding alloying element Ta are also discussed from the microscopic and macroscopic perspectives.

In situ study on plastic deformation mechanism of Al0.3CoCrFeNi high-entropy alloys with different microstructures

Al0.3CoCrFeNi high-entropy alloys (HEAs) have attracted the attention of researchers owing to their excellent mechanical properties. In this study, Al0.3CoCrFeNi HEAs with typical grain microstructures were fabricated and subjected to tensile tests, along with in situ scanning electron microscopy–electron backscatter deformation (SEM–EBSD), to determine the relationship between the grain microstructure, plastic deformation, and mechanical properties. The in situ EBSD analysis showed that the HEA sample with fine grains (FGs) exhibited more significant grain boundary deformation than that with coarse grains (CGs). The FG sample had a more uniform dislocation density distribution than the CG sample, and no noticeable excessive dislocation density was observed inside the grain. This indicates that the plastic deformation of the FG sample could be distributed more homogeneously without a prominent local stress concentration. Based on the grain structures from EBSD scans, crystal plasticity finite element modeling (CPFEM) and analysis were conducted to analyze the grain-level stress and strain heterogeneities. The results showed that during the tensile process, high stress was initially distributed near the B2 phase and subsequently at the grain boundaries of the HEA with increase in tensile deformation. The local stress distribution in the matrix was significantly affected by the B2 phase. Although high stress was distributed near the B2 phase during plastic deformation, the probability of crack initiation at the phase boundaries was low. This can be partly attributed to the formation of deformation twins at the junction of the B2 phase and FCC matrix, which releases the stress.

Crystal Plasticity Analysis for Kink Band Formation and Kink Strengthening

Crystal Plasticity Analysis for Kink Band Formation and Kink Strengthening

A framework to enable microstructure-sensitive location-specific fatigue life analysis of components and connectivity to the product lifecycle

Traditionally, aerospace components are treated as monolithic structures during lifing analyses, wherein distinct microstructural information at individual locations is not necessarily considered. In components with gradient microstructures, the resulting material allowables are conservative and associated with large uncertainty bounds. To improve precision in the life estimates, a location-specific lifing framework is developed, which tracks manufacturing processes and retrieves microstructural information at distinct locations for use within a crystal plasticity fatigue life prediction model. A use case for the lifing of a dual microstructure heat treated turbine disk component is demonstrated near the bore (fine grains) and rim (coarse grains) regions. We employ the framework to access (a) the grain size statistics and (b) the macroscopic strain fields to inform precise boundary conditions for the crystal plasticity analysis. The proposed location-specific lifing framework presents new opportunities for simultaneously designing the component and tailoring the microstructures to meet the targeted performance.

α-Mg/LPSO (Long-Period Stacking Ordered) phase interfaces as obstacles against dislocation slip in as-cast Mg-Zn-Y alloys

The influence of α-Mg/LPSO (Long-Period Stacking Ordered) phase interfaces on the flow stress of as-cast Mg-Zn-Y alloys was experimentally and numerically evaluated by compressive loading samples with different volume fractions of LPSO phase. The experimental results showed that the flow stresses of Mg-Zn-Y alloys with LPSO volume fractions ranging from 40 to 85% are clearly higher than those of single phase α-Mg or LPSO alloys. Comparison of deformation behavior between Mg-Zn-Y alloys and Mg-Zn-Y-Zr alloys, where Zr effectively decreases grain size of α-Mg phase, showed that the flow stresses of Mg-Zn-Y alloys with 25 and 40% of LPSO phase were insensitive to grain size whereas the flow stress of α-Mg single-phase alloy showed clear grain size dependence. By including the dependence of critical resolved shear stress (CRSS) on the average interface spacing, crystal plasticity analysis successfully reproduces the observed experimental stress-strain behavior, which suggests that α-Mg/LPSO phase interfaces are effective obstacles against dislocation slip in two-phase Mg alloys containing LPSO phase.