key: cord-0068151-b36hiw6b
authors: Sayahlatifi, Saman; Shao, Chenwei; McDonald, André; Hogan, James
title: 3D Microstructure-Based Finite Element Simulation of Cold-Sprayed Al-Al(2)O(3) Composite Coatings Under Quasi-Static Compression and Indentation Loading
date: 2021-10-05
journal: J Therm Spray Tech
DOI: 10.1007/s11666-021-01260-5
sha: 2813da195e2125c8a403a23efa998443b01fef25
doc_id: 68151
cord_uid: b36hiw6b

This study developed microstructure-based finite element (FE) models to investigate the behavior of cold-sprayed aluminum–alumina (Al-Al(2)O(3)) metal matrix composite (MMC) coatings subject to indentation and quasi-static compression loading. Based on microstructural features (i.e., particle weight fraction, particle size, and porosity) of the MMC coatings, 3D representative volume elements (RVEs) were generated by using Digimat software and then imported into ABAQUS/Explicit. State-of-the-art physics-based modeling approaches were incorporated into the model to account for particle cracking, interface debonding, and ductile failure of the matrix. This allowed for analysis and informing on the deformation and failure responses. The model was validated with experimental results for cold-sprayed Al-34 wt.% Al(2)O(3) and Al-46 wt.% Al(2)O(3) metal matrix composite coatings under quasi-static compression by comparing the stress versus strain histories and observed failure mechanisms (e.g., matrix ductile failure). The results showed that the computational framework is able to capture the response of this cold-sprayed material system under compression and indentation, both qualitatively and quantitatively. The outcomes of this work have implications for extending the model to materials design and for applications involving different types of loading in real-world application (e.g., erosion and fatigue).

). Among these reinforcing particles, Al 2 O 3 has been frequently used due to improved corrosion resistance and chemical stability ( Ref 14) . Recently, the Al-Al 2 O 3 composites fabricated by the cold spray additive manufacturing process have been used as protective coatings against wear, erosion, corrosion, and high temperature degradation in aerospace and other industrial sectors ( Ref 15, 16) . Among many deposition routes for producing coatings made of pure Al, cold spray stands out due to minimal heat loading of the substrate during the deposition process ( Ref 17) . In addition, this additive manufacturing method provides the possibility of producing multi-phase coatings via mixing feedstock powders by which the hard phases such as SiC and Al 2 O 3 can be incorporated effectively in the Al-MMCs coatings This article is an invited paper selected from presentations at the 2021 International Thermal Spray Conference, ITSC2021, that was held virtually May 25-28, 2021 due to travel restrictions related to the coronavirus (COVID- 19) pandemic. It has been expanded from the original presentation.

& Saman Sayahlatifi sayahlat@ualberta.ca (Ref 18) . These hard particles play a critical role in lowering the wear rate of the ceramic-metal coatings ( Ref 19) .

In research studies on experimental mechanics of ceramic-metal composite coatings, the behavior of coldsprayed MMC coatings has been extensively addressed in terms of dry sliding wear (Ref 20) , indentation (Ref 15) , flexural properties (Ref 21) , and erosion ( Ref 16) . However, there are a limited number of articles that investigate the response of MMC coatings through computational approaches, which is addressed in the current study. For example, Bolelli et al. (Ref 22) generated 2D RVEs based on the SEM images of WC-CoCr and WC-FeCrAl coatings to simulate ball-on-disk test and compression. The matrix and hard particles were modeled as elastic-plastic and pure elastic materials, respectively. The numerical results of Bolelli et al. (Ref 22) were compared with experiments based on the morphology of the worn surfaces and Young's modulus. In a separate study by Balokhonov et al. (Ref 23) , 2D models at micro-, meso-, and macroscales have been implemented by using the finite difference method for MMC coatings under tension and compression. It was found that curvilinear interfaces lead to stress concentration giving rise to the formation of shear bands in the Al matrix locally as well as cracking in the ceramic particles.

From a computational perspective, the majority of previous studies on Al-MMCs have focused on axial tensile loading, by which the microstructure has been modeled via 2D ( Ref 24) and 3D (Ref 25) RVEs. In a large number of studies, the occurrence of the three competitive damage mechanisms in particulate-reinforced Al matrix composites (PRAMCs) subject to tension, such as matrix ductile failure, matrix/particle debonding, and particle cracking, has been mainly explored by using phenomenological ductile failure criteria (Ref 25) , cohesive zone models (Ref 26) , and a conventional brittle cracking model (Ref 13) (i.e., elastic cracking behavior which employs the Rankine criterion for failure initiation (Ref 48)), respectively. For example, Zhang et al. (Ref 25) investigated the behavior of a 7vol.% SiCp/Al composite made by a stir casting technique and incorporated the three damage mechanisms in a real microstructure-based 3D RVE. The numerical results revealed that particle fracture and interfacial debonding emerged as the initial failure mechanisms in the composite under tensile loading.

In contrast to the numerous numerical studies that explore the tensile behavior of Al-MMCs, limited efforts have been made to address the indentation and compressive behavior computationally, particularly with emphasis on damage mechanisms. For example, Park 

In this study, pure Al and Al-Al 2 O 3 composite coatings were fabricated using a low-pressure cold spray system (SST series P, CenterLine Ltd., Windsor, ON, Canada), as shown schematically in Fig. 1(a) , which was connected to a volumetric powder feeder (5MPE, Oerlikon Metco, Westbury, NY, USA). Based on previous studies (Ref 2, 33, 34) , the air temperature and pressure were set to 375°C and 620 kPa, respectively. The nozzle was manipulated by a robot (Motoman HP-20, Yaskawa Electric Corp., Waukegan, IL, USA). The cold spray nozzle traversed across the Al substrate at a speed of 15 mm/s to transfer the feedstock powder to the substrate, and the deposition process produced five layers of the coating. The feedstock powder blend was developed through a three-step process: gas atomization, sieving, and mixing (see Fig. 1a ). Aluminum (99.0%) powder (CenterLine Ltd., Windsor, ON, Canada) and a-Al 2 O 3 with a purity of 99.5% (Amdry 6060, Oerlikon Metco Inc., Westbury, NY, USA) were used in this study. The Al and Al 2 O 3 powders were sieved to obtain a size distribution of 40-60 and 30-45 lm, respectively. The Al and Al 2 O 3 powders were admixed to produce powder blends containing 0, 60, and 90 wt.% Al 2 O 3 . This process was conducted using a cylinder with a 20 mm diameter whose angular velocity and operating time were set to 20 RPM and 30 minutes, respectively. As shown by Shao et al. (Ref 33) , when deposited into coatings, the mixed powder blend with 60 wt.% Al 2 O 3 produced coatings that were Al-34 wt.% Al 2 O 3 and the mixed powder blend with 90 wt.% Al 2 O 3 produced coatings that were Al-46 wt.% Al 2 O 3 .

As shown in Fig. 1(b) , the cold-sprayed coating deposits were cut into cuboidal specimens with dimensions of 2.3 mm in length, 2.7 mm in width, and 3.5 mm in height using wire electrical discharge machining. The samples were used for quasi-static compression testing, where the loading was applied in the direction of the 3.5 mm dimension. The experiments were conducted using the displacement control technique up to a maximum displacement of 1 mm at a constant rate of 1 9 10 -3 s -1 using an Instron 3365 testing machine (Instron, Norwood, Massachusetts, USA). To visualize the features of the macroscopic deformation of the specimen surface, the machine was equipped with an AOS PROMON U750 high-speed camera with a full resolution of 1280 9 1024 and a VIC 900170WOF LED laser light guide for illumination. This assembly was coupled with digital image correlation (DIC) capabilities using VIC-2D (v6 2018) software (Ref 35) (Correlated Solutions Irmo, SC, USA) to monitor the strain fields, which is detailed in Shao et al. (Ref 33) . The specimen was aligned between the loading platens made from M2-graded highspeed steel with a diameter of 1 inch (see Fig. 1b ), and extreme pressure grease was applied on the interfaces to eliminate the effect of friction and allow free lateral expansion. The compression tests were carried out as per ASTM Standard C1424-15 (Ref 36) at room temperature and repeated four times for each coating with different reinforcing particle content. To inform the microstructurebased models as related to the reinforcing particle content, porosity, particle shape, size, and distribution, microstructural characterization was done using a field-emission SEM coupled with energy-dispersive x-ray spectroscopy (EDS) operated at 20 kV (Zeiss Sigma, Oberkochen, Baden-Württemberg, Germany), as shown in Fig. 1(c) for the Al-46 wt.% Al 2 O 3 composite. The porosity of the samples was estimated using ImagePro software coupled with the SEM images, and the porosity was found to be 2.84 ± 0.31 vol.% in pure Al, 0.23 ± 0.04 vol.% in Al-34 wt.% Al 2 O 3 , and 0.17 ± 0.03 vol.% in Al-46 wt.% Al 2 O 3 . In addition, the EDS analysis revealed that the feedstock powders with 60 and 90 wt.% Al 2 O 3 led to depositions with 34 ± 2.56 and 46 ± 2.04 wt.% of ceramic particles, respectively.

A 3D FE model based on the coating microstructural features is presented to explore the behavior of Al-Al 2 O 3 MMC coatings under quasi-static compressive loading. The 3D representative volume elements (RVEs) were generated by the Digimat software for Al-34 wt.% Al 2 O 3 and Al-46 wt.% Al 2 O 3 MMCs. The RVEs were imported into the ABAQUS/Explicit solver (release 6.14). For the micro-indentation test, the homogenization approach (Ref 29) was applied and experimental compression data were used to extract the effective mechanical properties for each MMC coating sample.

RVEs with different sizes have been considered in previous studies (Ref 13, 37) . For example, Ma et al. (Ref 37) found no significant difference in the tensile stress-strain responses by varying the RVE size from 20 lm to 50 lm. In this study, an RVE length of 100 lm was chosen based on the microstructural features (e.g., average reinforcing particle size of 15 lm). The SEM images (see Fig. 1c and d) were first used to extract the distribution of particle size in the composites (e.g., the size of the alumina particles range from 1 to 30 lm in the Al-46 wt. % Al 2 O 3 composites (see Fig. 1c ). Next, the measured range of distribution was incorporated into the RVE using a uniform distribution in the Digimat software, which accounts for the variation and uncertainty in the particle size distribution that is likely to be observed through the SEM images from different locations of the sample. Additionally, the reinforcing ceramic particles represent an irregular shape in the SEM micrographs. Here, an icosahedron geometry was used to account for the shape of the particles, which has also been used to represent the irregular-shaped particles in previous studies involving MMC coatings (Ref [37] [38] [39] . The time step was set at 2 ls, which was found to meet the quasi-static loading condition ( Ref 40) . As shown in Fig. 2(a) , the top and bottom boundary faces have been fully restricted to the reference points (RPs) by the kinematic coupling constraints to facilitate application of load/ boundary conditions and obtain the stress-strain response of the RVE. A corner of the RVE was fully restricted to prevent the material from rigid boundary motion. The degrees of freedom of the bottom boundary face were fixed within all degrees of freedom, except for the in-plane displacements (i.e., Y-and Z-directions in Fig. 2b ). The same boundary conditions for application of compressive loading were also used in other studies (Ref 41, 42) . All of the constituents were discretized by 3D linear tetrahedral C3D4 elements. Following a mesh quality assessment to decrease the likelihood of element distortion at high strains, an average element size of 1.5 lm was used. On this basis, the RVE for Al-34 wt.% Al 2 O 3 and Al-46 wt.% Al 2 O 3 MMCs was meshed by 741,222 and 1,275,358 elements, respectively. Micro-indentation Vickers testing of the composite coatings was simulated via the homogenization approach (Ref 29). The effective mechanical properties, including the Young's modulus and flow stress, were extracted from the experimental compressive stressstrain histories for each particle concentration in the coatings and were an input into the approach. Figure 3 shows the FE model of the Vickers test. Due to symmetry, only one quarter of the homogenized block with symmetric constraints was modeled. The size of the block was determined as per the work of Shedbale et al. (Ref 29) to achieve convergence in the indentation response.

As shown by Shedbale et al. (Ref 29) , the Vickers indenter was considered as a discrete rigid body and fully confined, except for the vertical direction Y (see Fig. 3 ). The bottom surface of the block was fixed, and the lateral surfaces were free to deform. A frictionless contact was defined between the indenter and the top surface of the block, which was implemented by the standard surface-tosurface contact algorithm (Ref 29). By using an average element size of 5 lm, the block and the indenter were meshed by using 30,276 first-order eight-node 3D elements with reduced integration (C3D8R) and 2104 quadrilateral four-node 3D rigid elements (R3D4), respectively. Fig. 2 (a) Application of kinematic coupling between the boundary faces and the reference points (RP) in yellow color to apply compressive load and boundary conditions: All degrees of freedom were coupled to each other; (b) the boundary conditions applied on the RVE: The displacement control technique was applied to the RP in red color using a smooth amplitude to meet the quasi-static condition ;

where ; denotes the non-dilatational strain energy and q 1 , q 2 , and q 3 are the constants proposed by Tvergaard (Ref 48) to account for the effects induced by void interaction due to multiple-void arrays and to provide better consistency with experimental data. Here, r q and r y represent von Mises stress and the flow stress of the undamaged material. To model the rapid deterioration of stress carrying capacity caused by void coalescence, the parameter, f à , known as the effective porosity was first introduced by Tvergaard-Needleman ( Ref 30) . The function is specified as follows:

where f c is the critical void volume fraction (VVF) at the onset of the coalescence, f à u ¼ 1 q 1 corresponds to zero stress carrying capacity, and f F denotes the VVF when the material has completely failed, which governs the element deletion process. The increase in the VVF is deemed as the summation of the increment owing to void nucleation and the growth of existing voids. The function can be written as

Assuming plastically incompressible behavior for the material, the void growth rate (i.e., df growth ) can be expressed as a function of the plastic volume change as follows:

where de p ii denotes the trace of the plastic strain rate tensor. The nucleation of voids is considered to be exclusively dependent on the plastic strain, and it was assumed that occurrence of void nucleation occurred only under hydrostatic tension ( Ref 49, 50) . On this basis, the function is written as

where p represents the hydrostatic stress, f N is the void volume fraction of the nucleated void, e N is the mean equivalent plastic strain for void nucleation, and s N is the standard deviation of the distribution. Here, the rate of equivalent plastic strain,de p , is obtained by enforcing equality between the matrix plastic dissipation and the rate of macroscopic plastic work as follows:

Þr y : ðEq 7Þ Table 1 

where r à and r à i represent the normalized intact equivalent stress, r à f denotes the normalized fracture stress, and D is the damage variable, varying from 0 to 1. Here, r à ¼ r=r HEL , P à ¼ P=P HEL , T à ¼ T=P HEL , and _ e à ¼ _ e= _ e 0 , where r is the actual equivalent stress, r HEL is the equivalent stress at the Hugoniot elastic limit (HEL), P is the actual pressure, P HEL is the pressure at the HEL, T is the maximum tensile hydrostatic pressure tolerated by the material, _ e is the actual strain rate, and _ e 0 ¼ 1 is the reference strain rate. A, B, C, M, and N are material constants which need to be calibrated for each material. The maximum value of r à f is defined by SFMAX (i.e., the maximum limitation of the normalized fractured strength). Once the yield function is met as per Eq 11, the damage begins to accumulate based on the incremental equivalent plastic strain defined as

where r q , D 1 , and D 2 are deemed as material constants. To calculate pressure, P, a polynomial equation of state (EOS) is employed, which is defined as

where K 1 denotes the bulk modulus, K 2 and K 3 are material constants, g is the specific volume, U represents the internal energy which is related to the equivalent plastic flow stress r y by a quadratic expression, b is the fraction of the elastic energy loss converted to potential hydrostatic energy, and the shear modulus is shown by G. The 21 constants of the JH2 model for Al 2 O 3 were obtained from previous studies (Ref 54, 55) and are summarized in Table 2 . 

where T n , T s , and T t represent the tractions acting on the interface at a load increment in normal and in two in-plane shear directions, respectively. Likewise, T 0 n , T 0 s , and T 0 t denote the tractions at the onset of damage initiation in normal and in two in-plane shear directions. Note that the normal traction is tensile and pure compressive stress does not lead to decohesion. The components of the tractionseparation law are written as follows:

where T Ã n , T Ã s , and T Ã t are the stress components calculated by the elastic traction-separation behavior for the current strain prior to the damage initiation. D denotes the damage variable which begins to gradually increase from 0 to 1 with further loading once the debonding initiation criterion expressed by Eq 18 is met. The damage variable is defined as (Ref 58)

where d 0 m and d f m represent the effective separations at damage initiation and complete failure, respectively. The maximum value of the effective displacement during the loading process at each increment is shown by d max m . The effective separation at each load increment d m is calculated as (Ref 58)

where d n , d s , and d t are the nominal separations in normal and in two in-plane shear directions, respectively. To obtain the effective separation at complete decohesion, one can use the fracture energy G c , which is given as

The CZM constants used in this study are presented in Table 3 . Table 3 were selected to establish the best match between the experimental and numerical outcomes in this research study.

The numerically predicted results for Al-34 wt.% Al 2 O 3 and Al-46 wt.% Al 2 O 3 coatings under quasi-static compression are compared with those of the experiments in terms of the stress versus strain histories and observed failure mechanisms. This can provide insights for establishing an accurate computational framework to further explore the behavior of the material that can eventually give rise to a tool for material design and optimization. Figure 4 shows the predicted stress-strain responses in comparison with those measured by experiments. The pure Al and MMC samples were all experimentally tested in different directions, namely the nozzle traverse (travel) direction, the second in-plane direction perpendicular to the nozzle travel direction, and the deposition direction represented by X, Y, and Z, respectively, in Fig. 4 .

For the pure Al matrix, the results based on the data for the Z-direction were compared to experiments, as shown in the red solid curve in Fig. 4 . The predicted curve for the The cuboidal samples were all tested in three different directions denoted by X, Y, and Z corresponding to the nozzle moving direction, the second in-plane direction perpendicular to the nozzle moving direction, and the deposition direction, respectively. The dashed curves correspond to the experimental responses for each coating, and the solid curves represent the associated numerically predicted behavior pure Al matrix aligns with the experimentally measured one, which shows the accuracy of the approach for modeling the pure Al coating. Regarding the predicted responses for the MMCs, the model can reasonably capture the stiffness (i.e., the Young's modulus) and the maximum load bearing capacity of the composite coatings with different reinforcing particle concentrations. In addition, the experimental trend toward decreasing ductility with an increase in reinforcing particle content from 34 to 46 wt.% is reasonably reflected in the numerically predicted curves. Namely, plastic deformation in the Al-34 wt.% Al 2 O 3 composite coating begins to take place in the model at a strain of 0.6%, which leads to a yield stress of 141 MPa. Fig. 4.) In addition, as the strain exceeds 4%, matrix/particle debonding and a particle cracking failure mechanism manifest and develop with the increase in applied load within the RVE (see Fig. 5b and c) , particularly at the sharp corner and concaves of the particles (Ref 68) . This behavior can be attributed to the mismatch between the mechanical constants as well as the stress concentration at the curvilinear interfaces ( Ref 23) . Consequently, the flow stress remains almost constant from 5% strain to a strain of 15% and then rises slightly with a further increase in load up to the end of the loading cycle. This behavior is also reflected in the experimental curves, as matrix failure happens locally and does not lead to fracture of the sample (Fig. 4 -the dashed curves for the 34 wt.% Al 2 O 3 MMCs). From simulation, it can be implied that the spatial distribution of the particles affected by the number of particles and the mean free path parameter (i.e., inter-particle spacing of the reinforcing phase) (Ref 69)-which is determined by the weight percentage of the inclusions-does not lead to fracture of the Al-34 wt.% Al 2 O 3 MMC sample, since the number of thin ligaments is not critical enough to develop a 45°shear band (Ref 13, 68) , fracturing the specimen. This numerical implication (i.e., the microcracks in the matrix do not evolve to fracture the sample) is also corroborated by the experimental observation of the deformed sample at the end of the loading and the corresponding SEM micrograph shown in Fig. 5(d) . As shown, damage mechanisms such as ductile matrix failure and interfacial decohesion emerge locally, leading to the formation of dispersed microcracks that do not coalesce to cause failure in the sample at macrolength scales. For the Al-46 wt.% Al 2 O 3 composite, the predicted yield strain and yield strength are 0.7% and 253 MPa, respectively, while the measured yield strain varies between 0.79% and 0.83%, and the yield strength varies between 298 MPa and 317 MPa for the different coordinate directions. The larger discrepancy in the predicted yield stress of the Al-46 wt.% Al 2 O 3 MMC compared to that of the Al-34 wt.% Al 2 O 3 MMC can be another indication of the importance of including the cold spray-induced hardening and strengthening effect in the model in order to produce more accurate numerical results, especially for MMCs with a high percentage of particle reinforcement. Additionally, the earlier onset of the debonding failure mechanism in the model compared to the experiments can also play a role in the loss of stiffness prior to achieving peak load. Figure 6 and 7 shows a comparison between the predicted and experimentally observed failure mechanisms in the Al-46 wt.% Al 2 O 3 composite. As shown, the FE model can capture the occurrence of the three competitive damage mechanisms (i.e., matrix ductile failure, matrix/particle debonding, and particle cracking) of metal-ceramic coatings under compressive loading. In comparison with the MMC coating with 34 wt.% alumina reinforcement, the plastic strain is severely localized in the thin ligaments between the particles (see Fig. 6a ) in the model. The model predicts the formation of 45°shear cracks passing through the Al matrix between the particles as observed in SEM images, as shown in Fig. 7 . Once the strain exceeds 4%, particle cracking and matrix/particle debonding are initiated at the sharp corners of the particles (see Fig 6b and c)-which have been experimentally observed, as shown in Fig. 7 -and then propagate within the RVE. These failure showing the localized occurrence of damage mechanisms (e.g., matrix ductile failure and matrix/particle decohesion) at a micro-length scale, which does not lead to the coalescence of microcracks and global failure of the composite at the macroscale Fig. 6 The numerical qualitative results for the Al-46 wt.% Al 2 O 3 MMC shown at an axial strain of 4% and 10%: (a) The contour shows the distribution of void volume fraction in the Al matrix, which accumulates in the thin ligaments between the alumina particles forming * 45°shear cracks as the strain reaches 10%; (b) the spatial distribution of matrix/particle decohesion damage variable (CSDMG) which illustrates more severely debonding failure compared to the Al-34 wt.% Al 2 O 3 MMC (see Fig. 5b ). This results in loss of stiffness and load sustaining capacity as shown in Fig. 4 (see the solid blue curve); (c) the data illustrates the evolution of particle cracking initiating from the sharp corners within the RVE as the axial strain increases from 4% to 10% mechanisms are accompanied by matrix failure due to void growth in the thin ligaments (see Fig. 6a ). Once the strain exceeds 5%, the stress bearing capacity starts to decrease slightly and then remains constant up to a strain of 12% (Fig. 4 -the solid blue curve). This is a consequence of the development of the damage modes. The elements of the Al matrix in which the porosity has exceeded the critical value are removed from the mesh, leading to an abrupt decrease in load sustaining capacity (see Fig. 4 -the solid blue curve at a strain of *12%). This behavior is in agreement with the experimental trend that the material's load sustaining ability decreases after a given strain is reached. Overall, the reasonable agreement between the numerical and experimental findings in terms of stress-strain behaviors and failure mechanisms reveals the applicability of the model to conduct parametric studies that translate into tailoring particle and concentration size to control competition between failure mechanisms toward improving strength-density trade-offs.

The numerical outcomes of the homogenization approach were validated by Vickers hardness experiments. In the experiments, Vickers micro-indentation was applied to the samples with a load of up to 10 N as per ASTM Standard E384 (Ref 70). Figure 8(a) shows the plastically deformed area after complete unloading for the homogenized model of each MMC composite. From the figure, the diagonal length of the indented area decreased as the particle concentration increased, which results in a higher hardness. In other words, at a critical load, the composite material with a higher particle content is less deformed due to the enhanced stiffness and flow stress induced by the hard alumina particles. Figure 8 (b) illustrates the residual von Mises stress distribution for a load of 10 N after unloading in the homogenized model of Al-34 wt.% Al 2 O 3 MMC. The distribution pattern for different particle concentrations is the same, and the magnitude of the residual stress rises with an increase in the percentage of alumina particles. From Fig. 8(b) , the residual stress follows a continuous distribution as the model does not explicitly account for the microstructure, while the observations reported after using 2D heterogeneous models ( Ref 28, 71) showed that the residual stress is localized between the particles. This implies that 3D microstructure-based models are needed to study how the residual stress is developed in the material more realistically. The Vickers hardness of the numerical data was computed using (Ref 72):

where F represents the applied load and d is the diagonal length of the indented area. Figure 9 shows the numerically predicted Vickers hardness results in comparison with the experimental ones measured in three different directions, namely the nozzle travel direction, the deposition direction, and the third perpendicular direction represented by X, Z, and Y, respectively. As shown, the homogenized model Qualitatively, for the first time to the best of our knowledge, the manifestation and evolution of experimentally observed failure mechanisms in ceramic-metal coatings under compression (i.e., matrix ductile failure, matrix/particle debonding, and particle cracking) were all numerically captured through a 3D micromechanical finite element framework. This improves upon previous studies using 2D models (Ref 23, 54, 68) or single-particle 3D models ( Ref 11) . Additionally, the necessity of developing 3D models in this study was illustrated by Böhm et al. 

This study explored the behavior of Al-Al 2 O 3 composite coatings under quasi-static compression and indentation loading via FE analysis, both quantitatively (i.e., stress versus strain response) and qualitatively (i.e., the manifestation of damage mechanisms, including matrix ductile failure, interfacial debonding, and particle cracking). For the FE models, 3D RVEs were generated by Digimat software based on the microstructural features of the MMC coating samples with different particle concentrations, and the homogenization approach was employed for modeling the Vickers micro-indentation test. To account for the matrix ductile failure and the matrix/particle decohesion, the GTN model and the CZM approach were employed, respectively. The ceramic particles were modeled using the phenomenological JH2 model to incorporate particle damage accumulation. The FE model was validated by stress-strain histories, Vickers hardness, and damage mechanisms obtained experimentally, and a reasonable agreement was observed between the results. Altogether, the outcomes of this study confirm the applicability of the model to be used as a computational tool for spatially tailoring matrix and particle properties and geometries to develop high-performing gradient coating structures.

Engineering Research Council Canada, the Canada Foundation for Innovation, and the Province of Alberta Ministry of Jobs, Economy, and Innovation.

Fabrication of Aluminum-Alumina Metal Matrix Composites Via Cold Gas Dynamic Spraying at Low Pressure Followed by Friction Stir Processing

Comparison of 10 lm and 20 nm Al-Al 2 O 3 Metal Matrix Composite Coatings Fabricated by Low-Pressure Cold Gas Dynamic Spraying

Effect of a-Al 2 O 3 on the Properties of Cold Sprayed Al/a-Al 2 O 3 Composite Coatings on AZ91D Magnesium Alloy

The Influence of Cold and Detonation Thermal Spraying Processes on the Microstructure and Properties of Al-Based Composite Coatings on Mg Alloy

Quasistatic and Dynamic Compression of Aluminum-Oxide Particle Reinforced Pure Aluminum

Fabrication of Aluminium Metal Matrix Composites with Particulate Reinforcement: A Review. Mater. Today: Proc. 2017, 4

The Influence of Al 2 O 3 Particle Morphology on the Coating Formation and Dry Sliding Wear Behavior of Cold Sprayed Al-Al 2 O 3 Composites

Microstructure, Mechanical Properties and Corrosion Performance of 7075 Al Matrix Ceramic Particle Reinforced Composite Coatings Produced by the Cold Gas Dynamic Spraying Process

Creep-Fatigue and Cyclically Enhanced Cree p. Mechanisms in Aluminium Based Metal Matrix Composites

The Damage Mechanism of 17vol.%SiCp/Al Composite Under Uniaxial Tensile Stress

Microstructure-Based Analysis of Deformation and Fracture in Metal-Matrix Composite Materials

High Cycle Fatigue Behavior of the In-Situ TiB2/7050 Composite

Deformation Behavior and Damage in B4Cp/6061Al Composites: An Actual 3D Microstructure-Based Modeling

Effects of Al 2 O 3 on the Microstructures and Corrosion Behavior of Low-Pressure Cold Gas Sprayed Al 2024-Al 2 O 3 Composite Coatings on AA 2024-T3 Substrate

Cold Spray Aluminum-Alumina Cermet Coatings: Effect of Alumina Content

The Erosion Performance of Particle Reinforced Metal Matrix Composite Coatings Produced by Co-Deposition Cold Gas Dynamic Spraying

Cold Spraying-A Materials Perspective

A Review of the Mechanical and Tribological Behavior of Cold Spray Metal Matrix Composites

TEM Microanalysis of Interfacial Structures After Dry Sliding of Cold Sprayed Al-Al 2 O 3

Effect of Type of Reinforcing Particles on the Deposition Efficiency and Wear Resistance of Low-Pressure Cold-Sprayed Metal Matrix Composite Coatings

Cold Spraying SiC/Al Metal Matrix Composites: Effects of SiC Contents and Heat Treatment on Microstructure, Thermophysical and Flexural Properties

Microstructure-Based Thermo-Mechanical Modelling of Thermal Spray Coatings

A Numerical Study of Plastic Strain Localization and Fracture Across Multiple Spatial Scales in Materials with Metal-Matrix Composite Coatings

El-Shafei, A Random Microstructure-Based Model to Study the Effect of the Shape of Reinforcement Particles on the Damage of Elastoplastic Particulate Metal Matrix Composites

3D Microstructure-Based Finite Element Modeling of Deformation and Fracture of SiCp/Al Composites

Micromechanical Modeling of Damage in Elasto-Plastic Nanocomposites Using Unit Cell Representative Volume Element and Cohesive Zone Model

Three-Dimensional Microstructure Modeling of Particulate Composites Using Statistical Synthetic Structure and Its Thermo-Mechanical Finite Element Analysis

Simulated and Actual Micro-Structure Models on the Indentation Behaviors of Particle Reinforced Metal Matrix Composites

Heterogeneous and Homogenized Models for Predicting the Indentation Response of Particle Reinforced Metal Matrix Composites

Analysis of the Cup-Cone Fracture in a Round Tensile Bar

The mathematical theory of equilibrium cracks in brittle fracture

An Improved Computational Constitutive Model for Brittle Materials, AIP. Conf. Proc

High Strength Particulate Aluminum Matrix Composite Design: Synergistic Strengthening Strategy

Interfacial Heating During Low-Pressure Cold-Gas Dynamic Spraying of Aluminum Coatings

STM C1425-15, Standard Test Method for Monotonic Compressive Strength of Advanced Ceramics at Ambient Temperature

3D Micromechanical Simulation of the Mechanical Behavior of an In-Situ Al 3 Ti/A356 Composite

Computational Investigation of the Effect of Microstructure on the Scratch Resistance of Tungsten-Carbide Nickel Composite Coatings

3D Micromechanical Analysis of Thermo-Mechanical Behavior of Al 2 O 3 /Al Metal Matrix Composites

The Quasi-Static Behavior of Hybrid Corrugated Composite/Balsa Core Sandwich Structures in Four-Point Bending: Experimental Study and Numerical Simulation

An Experimental and Numerical Study of Novel Nano-Grained

The Mechanical Response of a a 2 (Ti 3 Al) ? c(TiAl)-Submicron Grained Al 2 O 3 Cermet Under Dynamic Compression: Modeling and Experiment

Modelling of Ductile Fracture in Single Point Incremental Forming Using a Modified GTN Model

Continuum Theory of Ductile Rupture by Void Nucleation and Growth: Part I-Yield Criteria and Flow Rules for Porous Ductile Media

Meso-Mechanics and Damage Evolution of AA5182-O Aluminum Alloy Sheet Based on the GTN Model

Numerical Determination of the Forming Limit Curves of Anisotropic Sheet Metals Using GTN Damage Model

Failure Analysis Based on Microvoid Growth for Sheet Metal During Uniaxial and Biaxial Tensile Tests

Influence of Void Nucleation on Ductile Shear Fracture at a Free Surface

Void Nucleation Effects in Biaxially Stretched Sheets

User's manual, Version 6.14, Dassault Systèmes

A Ductile Fracture Analysis Using a Local Damage Model

Experimental and Numerical Study of the Dynamic Response of B 4 C Ceramic Under Uniaxial Compression, Thin-Walled Struct

Ballistic Performance of Ceramic and Ceramic-Metal Composite Plates with JH1, JH2 and JHB Material Models

The Prediction of the Dynamic Responses of Ceramic Particle Reinforced MMCs by Using Multi-Particle Computational Micro-Mechanical Method

Back-Spalling Process of an Al 2 O 3 Ceramic Plate Subjected to an Impact of Steel Ball

Yielding of Steel Sheets Containing Slits

Analysis of a Rate-Dependent Cohesive Model for Dynamic Crack Propagation

Mixed-Mode Decohesion Finite Elements for the Simulation of Delamination in Composite Materials

Predictive Computational Model for Damage Behavior of Metal-Matrix Composites Emphasizing the Effect of Particle Size and Volume Fraction

A Review on Micromechanical Methods for Evaluation of Mechanical Behavior of Particulate Reinforced Metal Matrix Composites

Prediction of Interfacial Strength and Failure Mechanisms in Particle-Reinforced Metal-Matrix Composites Based on a Micromechanical Model

Development of a Molecular Dynamic Based Cohesive Zone Model for Prediction of an Equivalent Material Behavior for Al/ Al 2 O 3 Composite

Multiple Strengthening Mechanisms of Cold-Sprayed cBNp/NiCrAl Composite Coating

Size Effect on the Shear Damage Under Low Stress Triaxiality in Micro-Scaled Plastic Deformation of Metallic Materials

Enhancing Tensile and Compressive Strengths of Magnesium Using Nanosize (Al 2 O 3 ? Cu) Hybrid Reinforcements

Nanomechanics of Hall-Petch Relationshi p

Investigating Mesh Sensitivity and Polycrystalline RVEs in Crystal Plasticity Finite Element Simulations

Numerical Analysis on the Effects of Particle Configuration on the Damage and Mechanical Properties of Particle Reinforced MMCs Under Dynamic Compression

On the Microstructure-Dependency of Mechanical Properties and Failure of Low-Pressure Cold-Sprayed Tungsten Carbide-Nickel Metal Matrix Composite Coatings

Effects of Random Particle Dispersion and Size on the Indentation Behavior of SiC Particle Reinforced Metal Matrix Composites

ISO 6507-1: Metallic materials-Vickers hardness test-Part 1: Test method

Characterization of Indentation-induced 'Particle Crowding' in Metal Matrix Composites

An Enhanced Finite Element Model Considering Multi Strengthening and Damage Mechanisms in Particle Reinforced Metal Matrix Composites

Three-Dimensional Multi-Particle FE Model and Effects of Interface Damage, Particle Size and Morphology on Tensile Behavior of Particle Reinforced Composites

Effect of Reinforcement Shape on Fracture Behaviour of SiC/Al Composites with Network Architecture

Simulations of Deformation and Damage Processes of SiCp/Al Composites During Tension

Particle Distribution-Dependent Micromechanical Simulation on Mechanical Properties and Damage Behaviors of Particle Reinforced Metal Matrix Composites

Toroghinejad, Refinement of Microstructure and Improvement of Mechanical Properties of Al/Al 2 O 3 Cast Composite by Accumulative Roll Bonding Process

Properties of Al-Al 2 O 3 Composites Synthesized by Spark Plasma Sintering Method

Investigation of Particle Size and Amount of Alumina on Microstructure and Mechanical Properties of Al Matrix Composite Made by Powder Metallurgy

Effect of Reinforcement Concentration on the Properties of Hot Extruded Al-Al 2 O 3 Composites Synthesized Through Microwave Sintering Process

Comparisons Between Three-Dimensional and Two-Dimensional Multi-Particle Unit Cell Models For Particle Reinforced Metal Matrix Composites

Impact of 3D-Model Thickness on FE-Simulations of Microstructure

Automatic Generation of 2D Micromechanical Finite Element Model of Silicon-Carbide/Aluminum Metal Matrix Composites: Effects of the Boundary Conditions

A Homogenization-Based Damage Model for Stiffness Loss in Ductile Metal-Matrix Composites

The Effect of the Standoff Distance on the Microstructure and Mechanical Properties of Cold Sprayed Cr3C2-25(Ni20Cr) Coatings

Size-Dependent Compression Deformation Behaviors of High Particle Content B4C/Al Composites

A Framework for Automated Analysis and Simulation of 3D

Part 1: Statistical Characterization

Particle Interspacing Effects on the Mechanical Behavior of a Fe-TiB 2 Metal Matrix Composite Using FFT-Based Mesoscopic Field Dislocation Mechanics

EBSD-Based FEM Simulation Of Residual Stresses in a WC6wt.-%Co Hardmetal

Towards Optimization of Thickness, Hardness, and Porosity of Low-Pressure Cold Sprayed WC-Ni Coatings

Effect of Reinforcement Particle Size on Quasistatic and Dynamic Mechanical Properties of Al-Al 2 O 3 Composites

Effects of Particle Shape on the Macroscopic and Microscopic Linear Behaviors of Particle Reinforced Composites

The Influence of Particles Size and Its Distribution on the Degree of Stress Concentration in Particulate Reinforced Metal Matrix Composites

Acknowledgments The authors gratefully acknowledge funding support from Imperial Oil (Esso), the Natural Science and J Therm Spray Tech