Microstructure Of Metal Matrix Composites Research Articles

Adapting high-speed indentation mapping for investigating microstructure-property correlations in chromium carbide-nickel alloy coatings: Challenges and solutions

This study investigates the microstructural and mechanical characteristics of chromium carbide‑nickel rich alloy coatings produced through laser cladding, detonation spraying, and plasma spraying techniques. While all three processing techniques used the same feedstock powder, each method yields coatings with unique microstructures encompassing varying compositions and length scales. Employing Field Emission Scanning Electron Microscopy (FE-SEM) in combination with Energy Dispersive Spectroscopy (EDS) and nanoindentation mapping, local microstructure and mechanical properties were assessed at the micrometre length scale. Laser-clad coatings exhibit a typical metal matrix composite microstructure with high carbide content, distinct (MoNb)C2 phases, and Fe in the metallic matrix, while the thermal sprayed coatings showed carbides of varying sizes and metallic matrix with varying degrees of chromium dissolved in it. The instrumented indentation technique helped precisely record the microstructural features in all the coatings. Chromium carbide consistently emerges as the hardest phase across all coatings, with variations in metallic matrix hardness. Higher matrix hardness in thermal sprayed coatings correlates with increased Cr content, attributed to extended solid solubility of Cr and the presence of Mo and Nb. Energy dispersive spectroscopy and transmission electron microscopy provided clearer insight into the microstructure. This study highlights a direct one-to-one correlation between microstructure and mechanical properties mapped using instrumented indentation techniques in chromium carbide‑nickel rich coatings across different deposition methods.

Optimization of friction stir processing parameters for improving structural and mechanical properties in in situ AA5083-H111/Al–Fe composites

The primary focus of this study is the application of friction stir processing to produce surface composites of in situ AA5083-H111/Al–Fe. These composites were fabricated by mixing mechanically alloyed Fe–40 wt% Al powder for 40 h. The AA5083 substrate underwent a two-pass friction stir processing with changes in the tool’s movement direction during fabrication. This experiment used Taguchi’s L9 orthogonal array design to gather and analyse data efficiently. Following each friction stir processing pass, the fabricated aluminium metal matrix composite microstructure, hardness and ultimate tensile strength were conducted. In this study, the maximum tensile strength of 225.8 MPa after the first pass and 253.6 MPa after the second pass. Additionally, microhardness measurements indicated values of 123.3 and 128.3 Hv after the first and second passes, respectively. These impressive mechanical properties were achieved by optimizing specific process parameters, including a tool shoulder diameter of 21 mm, a tool rotational speed of 900 rpm, a tool traverse speed of 63 mm/min and a tilt angle of 1.5°. Furthermore, examining the fracture surface of the friction stir processed sample revealed ductile failure behaviour, suggesting that the material experienced deformation and stretching before fracture. This observation aligns with the inherent ductile nature of the AA5083/Al–Fe composite.

Simulation of ductile crack propagation in metal matrix composites ‐ Comparison with cyclic experiments

AbstractThe efficient operation of mechanized tunnel drilling machines is strongly determined by the wear resistance of the applied mining tools. Especially in chisels, but also partly in cutting disks, metal matrix composites are used. Their wear mechanism is dominated by surface spalling, i.e. subcritical crack propagation through the material's microstructure, mainly consisting of a ductile metal matrix and carbide inclusions. Since this process is primarily governed by the morphology of the microstructure and the mechanical behavior of the individual phases, simulations at the microscale enable the design of improved materials. In this contribution, a method for the modeling of this process is presented. The approach is based on the eigenerosion framework introduced in [1] and an algorithmic scheme for large strains is given, which extends the small strain implementation in [2]. For the phases at the microscale, the finite strain plasticity formulation [3] is applied. Examples according to [4] are shown in order to demonstrate the mesh independence of the framework for ductile crack propagation. Furthermore, simulations are carried out on the microscale by applying the Finite Cell Method [5] on metal matrix composite microstructures. Here, a specific cell arrangement is constructed which minimizes the required number of cells for a given microstructure morphology. Additionally, an experimental setup for the validation of the eigenerosion framework on the microscale is presented. By evaluating the results of these simulations, failure of the material can be investigated on a microscopic level and improvements of the material morphology regarding wear can be realized.

Microstructure-based analysis of residual stress concentration and plastic strain localization followed by fracture in metal-matrix composites

A numerical study is performed to investigate the deformation and fracture in metal matrix – ceramic particle composites using Al6061T6 and ZrC as an example of the compound materials. The step-by-step packing method is adopted for generating three-dimensional model microstructures of metal-matrix composites, with the irregular shape of particles and polycrystalline structure of the matrix being taken into account. The dynamic boundary-value problems are solved by the finite-element method. Constitutive models describing the mechanical behavior of the composite compounds include anisotropic elasticity, crystal plasticity with the strain hardening and strain fracture criterion for the matrix and isotropic elastic-brittle formulation with the stress fracture criterion for particles. A user-defined subroutine is developed to combine the anisotropic matrix and isotropic particle responses and implemented in the finite element calculations of the composite thermomechanical behavior. The interrelated plastic strain localization in the aluminum matrix and crack origination and growth in the matrix and ceramic particle are investigated under compression and tension, including the influence of the cooling-induced residual stresses. A detailed analysis is performed to evaluate the residual stress concentration in local regions of bulk tension formed under all-round and uniaxial compression of the composite due to the concave and convex interfacial asperities.

Analyzing the Effect of Particle Shape on Deformation Mechanism during Cutting Simulation of SiC P/Al Composites.

To analyze the effect of particle shape on deformational behavior in the cutting simulation process for metal matrix composites (MMCs), two 2D mesoscopic-based finite element (FE) models reinforced with randomly distributed circular and irregular polygonal particles were developed. Different material properties (metal matrix phase, particle reinforced phase) and the properties of the particle–matrix interface were comprehensively considered in the proposed FE model. Systematic cutting experiments were conducted to compare the differences between two modeling approaches with respect to particle fracture, chip formation, cutting force and surface integrity. The results show that the irregular polygonal particle model is closer to the microstructure of MMCs, and is better able to reflect the deformation behavior of particles. The simulation model with irregular polygonal particles is even able to capture more details of the impact caused by particles, reflecting variations in the cutting force in the actual cutting process. The initiation and propagation of microcracks is mainly determined on the basis of particle geometry and further affects chip formation. Both models are able to correctly reflect surface defects, but the irregular polygonal particle model provides a more comprehensive prediction for the subsurface damage of MMCs.

PENGARUH VARIASI TEKANAN DAN SUHU PADA PENGADUKAN SERBUK ALUMINIUM (Al), MAGNESIUM (Mg), DAN SENG (Zn) TERHADAP SIFAT MEKANIK LOGAM DENGAN METODE METALURGI SERBUK

The use of aluminum is often found The mechanical properties of aluminum that arelightweight and rust resistant are among the reasons aluminum is often used for certainraw materials. However, the mechanical properties of aluminum if the levels are pure willnot correspond to the intended use, because the hardness value is very small. Thereforealuminum to add mechanical properties need to be added to other alloy compounds. Thisresearch is focused on Magnesium (Mg and Zinc (Zn) compounds with levels of variation ofboth aluminum 95%, magnesium 2.5%, 2.5% zinc. tons and temperature 550 ° C (2)pressure 10 tons and temperature 570 ° C (3) pressure 12 tons and temperature 590 ° C.From each impact test, hardness and tensile variations of the third which has the highestvalue. From the picture above, it can be seen that the spread in the pressure andtemperature variations in each Metal Matrix Composite (MMC) specimen. there is novariation in the MMC microstructure.

Laser power influence on track’s geometry and microstructure aspects of Fe and Sn-based alloy processed by directed energy deposition

Additive manufacturing of metal matrix composite (MMC) is a challenging field to explore. Besides components’ geometric constitution, requirements related to final microstructures must be met. Depending on the application, such as tribology, machining, or magnetism related, there is a need to preserve a specific phase, which is generally responsible for the engineering function of the fabricated component. This work analyzes the laser power (P) parameter influence on track’s geometry and microstructure aspects of Fe and Sn-based alloy processed by directed energy deposition (DED). Objectives are observing the interaction between Fe-α and Sn-based alloy as a function of P and, then, define a processing window that allows the MMC microstructure. Experimental methodology relied on single-tracks bead-on-plate deposits with P variations. To assess track’s geometry and microstructure changes, postprocessing analyses were performed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Results show that P influences positively on tracks’ height, width, and cross section area. Greater laser power resulted in higher geometric aspects. Microstructure evolution was observed as P was enhanced from 150 to 700 W. In lower P ranges, Fe particles are not strongly affected by the heat source, resulting in an MMC microstructure mainly composed by Fe-α dispersed on a Sn-rich alloying matrix. When more thermal energy is provided due to higher laser power levels, Fe and Sn diffuse to a greater extent, resulting in an increased quantity of Fe-Sn phases and a more homogeneous microstructure. EDS mapping suggests that formed phases are Fe solid solutions containing Sn. Then, it is concluded that MMC microstructures are possible to be achieved around a P window of 150 W.

Mechanical damage behavior of metal matrix composites with the arbitrary morphology of particles

Metal matrix composites have significant applications in the engineering field. During service, the fracture is one of the most typical failure modes. In this study, the digital image-based technique (DIT) combined with a micro-scale damage cohesive finite element model (CFEM) was employed to reconstruct the microstructures of metal matrix composites with the arbitrary morphology of particles. The cohesive finite element in this model can predict the process of crack initiation and propagation spontaneously, and the effectiveness of the model was verified by the in-situ tensile tests of the compacted graphite iron (CGI) sample. We found that the morphology and distribution of the graphite particles play important roles in crack initiation and propagation under tensile and compressive loadings. The relationship between the graphite particle size and yield strength was established, and an optimal graphite particle size was found for the maximum yield strength, which is different from the previous results. The relationship between microstructures and tensile properties of CGI could contribute to the design and development of metal matrix composites with optimal mechanical properties.

Influence of Molding Pressure on Properties of Al<sub>2</sub>O<sub>3</sub>- Al Composite Materials Sintered via Vacuum Sintering Method

In this paper, the effect of raw materaisl on the properties of coated Al2O3/Al cermet materials were investigated, the raw materials were prepared via different methods, which provide a reference for obtaining higher performance cermet materials. Through mixing, molding, sintering, sample preparation, scanning electron microscopic observation, energy spectrometer observation and analysis, the following conclusions can be drawn, the density of the composite material increases first and then decreases with the increase of the molding pressure. When the molding pressure is 30 MPa, the density of the composite material reaches the maximum value, that is 93.5%. The greater the applied pressure, the more compact the aluminum powder and alumina powder, and the longer the tissue composition, the more uniform. there is no crack in the c-picture, and there are cracks in the a and b pictures. The microstructure of metal matrix composites prepared at different molding pressures is also different. Sintering of the green body formed at 30 MPa resulted in relatively few cracks and voids in the material. The surface hardness of the composite material increases first and then decreases with the increase of the molding pressure, and the surface hardness of the composite material reaches a maximum value (875 HV) at a molding pressure of 30 MPa.

3D Network Structure TiNNP/Ni Composite with High Tensile Strength and Ductility Simultaneously

Tailoring microstructure of metal matrix composites can achieve superior mechanical properties, especially for the plasticity. In this work, both pure Ni and the 3D network structure TiNNP/Ni composites are synthesized through the combination of low energy balling and spark plasma sintering, with the same process. The strength of the 3D structure TiNNP/Ni composites improved from 180 MPa to 690 MPa while the ductility is as high as the pure Ni prepared.

Effect of amorphous silica by rice husk ash on physical properties and microstructures of recycled aluminium chip AA7075

AbstractHigh strength to weight ratio of aluminium reinforced as metal matrix composites is a well known material used in automotive application. The effects of recycled aluminium chips AA7075 with amorphous silica by rice husk ash on the physical properties and microstructure were investigated. Recycled aluminium chip AA7075 was reinforced with agro waste of amorphous silica rice husk ash i. e., 2.5 %, 5 %, 7.5 %, 10 % and 12.5 %. Samples of these metal matrix composites were prepared by cold compaction method due to the lower energies consumption and operating cost compared to conventional recycling by casting. Physical testing of density, apparent porosity, water absorption and hardness tests of the metal matrix composites samples were examined in the current study. The density of metal matrix composites was increased up to 5 % of amorphous silica, and then decreased with increasing mass fraction of amorphous silica. Porosity and water absorption of metal matrix composites were significantly consistent at increasing mass fraction of amorphous silica, while the hardness of metal matrix composites was increased at increasing amorphous silica. Consequently, the microstructures of metal matrix composites were observed via optical microscope to analyze the dispersion of the reinforced composites. The microstructures of metal matrix composites were found non‐homogeneous and random distribution of amorphous silica and aluminium chip AA7075 compared to 100 % recycled aluminium chip AA7075. Based on investigation to aluminium reinforced rice husk ash composites, it has good potential to improve the material behavior of metal matrix composites by appropriate composition amorphous silica to composite.

3D Visualized Characterization of Fracture Behavior of Structural Metals Using Synchrotron Radiation Computed Microtomography

Synchrotron radiation computed micro-tomography (SR-μCT) is a non-destructive characterization method in materials science, which provides the quantitative reconstruction of a three-dimension (3D) volume image with spatial resolution of sub-micrometer level. The recent progress in brilliance and flux of synchrotron radiation source has enabled the fast investigation of the inner microstructure of metal matrix composites without complex sample preparation. The 3D reconstruction can quantitatively describe the phase distribution as well as voids/cracks formation and propagation in structural metals, which provides a powerful tool to investigate the deformation and fracture processes. Here, we present an overview of recent work using SR-μCT, on the applications in structural metals.

Evaluation Microstructure and the Mechanical Properties of Composite Material for Al-Matrix Reinforced by Ceramic Materials (Sic And Al2O3)

In this investigation, the mechanical properties and microstructure of Metal Matrix Composites (MMCs) of Al.6061 alloy reinforced by ceramic materials SiC and Al2O3 with different additive percentages 2.5, 5, 7.5, and 10 wt.% for the particle size of 53 µm are studied. Metal matrix composites were prepared by stir casting using vortex technique and then treated thermally by solution heat treatment at 530 0C for 1 hr. and followed by aging at 175 0C with different periods. Mechanical tests were done for the samples before and after heat treatment, such as impact test, hardness test, and tensile test. Also, the microstructure of the metal matrix composites was examined by optical microscopy before and after heat treatment. The results of this work showed that precipitation of Mg2Si as a secondary phase and improvements in mechanical properties with increase in the percentage of SiC and Al2O3. Also, the results of SiC revealed an improvement in mechanical properties more than for Al2O3 such as hardness, impact strength, yield strength, tensile strength, increasing the plasticity constant (k) and decreasing the strain hardening exponent (n).

Microstructure metrics for quantitative assessment of particle size and dispersion: Application to metal-matrix composites

Homogeneous dispersion of reinforcement particles within a matrix is of paramount importance for achieving high quality metal-matrix composite (MMC) materials. This paper develops a protocol for quantitative evaluation of particle size and dispersion in MMC microstructures. The protocol is based on statistical analysis of features in micrographs and embedding the information into a suitably defined microstructure homogeneity metric (H-metric) and a particle size distribution metric. Every micrograph undergoes the K-means clustering algorithm for accurate separation of phases before it is used in calculation of the metrics. Finally, the protocol relies on analysis of variance to verify the meaningfulness of results. The protocol is applied to study homogeneity and particle size distribution in MMCs consisting of Cu-matrix with 20vol.%-SiC The composites were processed using high pressure torsion and double torsion to a different number of torsional turns. During processing, particles fragment and form clusters of fragments. As straining continues, the clusters of fragments disperse in the matrix. A decrease and then increase of the H-metric demonstrate that the metric can pick up these processes occurring in the microstructure. The analysis reveals a strong correlation between the particle dispersion homogeneity and particle size distribution. The protocol developed herein can facilitate the design of MMCs with superior properties through engineering optimal homogeneity and particle size distributions in function of process variables.

A Numerical Analysis of Deformation Processes in Oxide Dispersion-Strengthened Materials - Influence of Dislocation-Particle Interactions

A recently developed 3D discrete dislocation dynamics (DDD) model is employed to study kinetics of dislocation ensembles subjected to high temperature creep in microstructures of metal matrix composites. We particularly focus on a migration of low angle tilt boundaries in a field of rigid impenetrable particles. This type of dislocation boundaries represents a typical microstructural feature mediating plastic deformation during the high temperature loadings. The article compares results of numerical studies that considered distinct dislocation-particle in-teractions in order to describe the response of dislocation structure to the applied stress. The resultssuggest that, regardless the details related to the dislocation-particle interactions, a critical applied stress always exists, below which the boundary migration process ceases [1,2]. The existence of crit-ical threshold is confirmed by creep tests of ODS materials. This critical threshold, contrary to theclassical Orowan stress, is proportional to the dislocation density. The displacements of individual dislocation segments on the micro-scale level reflect the changes in the dislocation-particle interactions quite sensitively. Atthemacro-scale level, the overall strain rate, which averages out velocities of all the individual dislocation segments, is also significantly influenced by the changes in dislocation-particle interaction

Compressive and tensile deformation behaviour of TRIP steel-matrix composite materials with reinforcing additions of zirconia and/or aluminium titanate

The mechanical properties and the related microstructure of metal-matrix composites (MMC) based on a high-alloyed CrMnNi steel with varying particle reinforcements (5% or 10 vol%) of magnesia partially stabilized zirconia and/or aluminium titanate were investigated. The powder metallurgical processing comprised the cold extrusion and conventional solid-state sintering at 1350 °C. The mechanical properties were examined by quasi-static compressive and tensile loading tests at ambient temperature. The microstructure characteristics contributing to significant changes in strength and ductility and affecting the failure mechanisms during deformation were characterised by scanning electron microscopy including energy-dispersive X-ray spectroscopy and electron backscatter diffraction, and by X-ray diffraction. For all compositions the stress-strain and the deformation behaviour were mainly controlled by dislocation hardening and α’-martensite formation in the steel matrix, but it was further improved by the particle strengthening of the ceramic reinforcement. Thus, the composite materials showed higher strength and work hardening than unreinforced steel specimens over a wide strain range. The pressureless sintering triggers several reactions at the metal/ceramic interface, which leads to pronounced destabilisation of the initial metastable zirconia particles with a lack of transformation toughening capability, and the formation of invalid olivine. These MMC suffer from early particle/matrix displacement and particle fracture under loading. A more positive effect of interfacial reactions was observed in the composites with addition of aluminium titanate. Here, the formation of a dense spinel structure and the reliable matrix/particle interface bonding during firing provides a significant particle strengthening effect. The combination of zirconia and aluminium titanate provides mechanical and microstructural benefits as well. Thus, aluminium titanate facilitates the consolidation of powder metallurgical processed steel-matrix MMCs via the conventional sintering for advanced load applications. The results of the study help to understand essential hardening mechanisms in composite materials and provide potential for future cellular MMC structures.

Free-standing silver/carbon nanotube metal matrix composite thin films

Advanced metal matrix composite (MMC) thin-film electrodes were fabricated utilizing single-wall carbon nanotubes (SWCNTs) as a reinforcement material. The MMCs were embedded with SWCNT thin films of 10, 20, and 50 nm thicknesses between thermally evaporated 1.5 µm Ag layers. A method has been developed to release the MMCs as free-standing films, and tensile testing was performed to evaluate the mechanical properties. The MMC containing a 20-nm SWCNT layer achieved a ~30 % increase in ultimate tensile strength, and a ~100 % increase in strain-to-failure, resulting in a ~150 % increase in toughness compared to Ag control samples. Scanning electron microscopy (SEM) analysis of the MMC microstructure revealed a decrease in Ag grain size with increased SWCNT loading, which correlated with the mechanical performance to identify the critical range of SWCNT layer thicknesses to achieve reinforcement. SEM also revealed SWCNTs protruding more than 1 μm from the fracture edges, indicating the potential of the MMCs to bridge micro-cracks in electrodes. The collective results show promise for SWCNT MMCs as an advanced electrode material capable of bridging micro-cracks in solar cells and flexible electronics.

Effect of Equal Channel Angular Pressing on Microstructure and Mechanical Properties of As-Cast Al-B<sub>4</sub>C Composite

In this experiment, comparison analysis of mechanical properties, porosity and grain size of Pure Al (powder), 95%AL + 5% B4C (With sand casting method) and 95%AL + 5% B4C (With ECAP method) are determined. The ECAP method value is much greater than the sand casting method,because of metal matrix composite microstructure refinement during the pressing operation. Because of material porosity value decreases, powder particle consolidation, the closure of porosity, grain refinement and improve in dislocation occurs as ECAP method gives the results of Mechanical properties as like tensile strength 105.8Mpa, Hardness 94HV, density 888.88kg/m3values increase. At the same time, porosity and grain size value will be reduced because of individual power consolidation happening during ECAP methods like as 1.63% and 8μm. In this metal matrix composite is applied to aeronautical and automobile industry

Effect of Pass Number, Rotational and Traverse Speed on Particle Distribution and Microstructure of AZ31/SiC Composite Produced by Friction Stir Processing

In this paper, Friction Stir Processing (FSP) is used to produce a homogenous AZ31/SiC Metal Matrix Composite (MMC). The product could be used in industries such as aerospace, which needs materials with a high strength to weight ratio. AZ31B magnesium alloy plates and about 5 vol % SiC powder are selected as matrix and reinforcement particles, respectively. The effect of the number of FSP passes, the rotational and traverse speed on the particle distribution and the matrix microstructure of MMC are investigated. Optical microscopy is used to observe both particle distribution and matrix microstructure. The results show that a perfect particle distribution with no defect can be achieved at very low rotational and transverse speeds which are 300 rpm and 15mm/min. Moreover, the number of passes significantly improves the particle distribution. The mean grain size decreases from 9.5 μm to 1.95μm for a 4-pass MMC.

Effect of starting material character and its sintering temperature on microstructure and mechanical properties of super hard Ti/TiB metal matrix composites

Different concepts and processing paths were investigated to minimize large scale production costs occurring for new growing interest group of in situ metal matrix composite (MMC) materials. High inputs dependently directly from a composition and disability to fabricate near net shape part elements result mainly from a few step procedures connected often with increasing machining costs. Nevertheless different compositions of MMC materials followed by the same broad spectrum of properties show enormous potential perspectives for diverse range of application. Present in realized research comparison of starting material character and adopt heat treatment temperatures evidence microstructure and mechanical properties. Starting precursor grain size scale influence available energy for phase transformation or base substrate reaction, furthermore it determines obtained in realized processes MMC microstructure its homogeneity, porosity level and final properties that result from above. Obtained from realized research conclusions in the examined case could be directly transferred to whole family of MMC materials.