Metal Matrix Phase Research Articles

Constitutive modeling of two-phase metallic composites with application to tungsten-based composite 93W–4.9Ni–2.1Fe

The two-phase metallic composites, composed by the metallic particulate reinforcing phase and the metallic matrix phase, have attracted a lot of attention in recent years for their excellent material properties. However, the constitutive modeling of two-phase metallic composites is still lacking currently. Most used models for them are basically oriented for single-phase homogeneous metallic materials, and have not considered the microstructural evolution of the components in the composite. This paper develops a new constitutive model for two-phase metallic composites based on the thermally activated dislocation motion mechanism and the volume fraction evolution. By establishing the relation between microscopic volume fraction and macroscopic state variables (strain, strain rate and temperature), the evolution law of volume fraction during the plastic deformation in two-phase composites is proposed for the first time and introduced into the new model. Then the new model is applied to a typical two-phase tungsten-based composite – 93W–4.9Ni–2.1Fe tungsten heavy alloy. It has been found that our model can effectively describe the plastic deformation behaviors of the tungsten-based composite, because of the introduction of volume fraction evolution and the connecting of macroscopic state variables and micromechanical characteristics in the constitutive model. The model's validation by experimental data indicates that our new model can provide a satisfactory prediction of flow stress for two-phase metallic composites, which is better than conventional single-phase homogeneous constitutive models including the Johnson–Cook (JC), Khan–Huang–Liang (KHL), Nemat-Nasser–Li (NNL), Zerilli–Armstrong (ZA) and Voyiadjis–Abed (VA) models.

Fracture toughness and corrosion behaviour of infiltrated Al2O3|P – Steel composites

In the present study, the fracture toughness and the corrosion behaviour of particle reinforced alumina–steel composites were investigated. Composites, only differing in their type of matrix steel, were produced by Ti-activated pressureless infiltration. The aim was to clarify the influence of the matrix phase on the electrochemical properties as well as on the fracture toughness of the composites. Results show that the corrosion resistance of the composite mainly depends on the steel matrix. The processing history of the matrix steel is determining. Melt-processing decreases the corrosion resistance. All composites exhibit failure-tolerant behaviour. Though, local differences in the matrix plasticity on the micro-scale have been observed. Failure occurs primarily through Al2O3-particles. The increase in resistance against crack propagation, from about 8 to more than 30MPam1/2 after 1mm crack extension, is attributed to the metallic matrix phase remaining intact behind the propagating crack front.

Effect of Cobalt Content on Wear and Corrosion Behaviors of Electrodeposited Ni–Co/WC Nano-Composite Coatings

Metal-ceramic composite coatings are widely used in automotive and aerospace industries as well as micro-electronic systems. Electrodeposition is an economic method for application of these coatings. In this research, nickel-cobalt coatings reinforced by nano WC particles were applied on carbon steel substrate by pulse electrodeposition from modified Watts bath containing different amounts of cobalt sulphate as an additive. Saccharin and sodium dodecyl sulphate (SDS) were also added to electroplating bath as grain refiner and surfactant, respectively. The effect of cobalt content on wear and corrosion behavior of the coatings was investigated. Wear and corrosion properties were assessed by pin-on-disk and potentiodynamic polarization methods, respectively. Phase analysis was performed by X-ray diffraction (XRD) using CuK(alpha) radiation and the worn surfaces were studied by means of Scanning Electron Microscopy (SEM). The results showed that the addition of cobalt improved the wear resistance of the coatings. In the presence of 18 g/L cobalt in electrodeposition bath, the wear rate of the coating decreased to 0.002 mg/m and the coefficient of friction reduced to 0.695 while they were 0.004 mg/m and 0.77 in the absence of cobalt, respectively. This improvement in wear properties can be attributed to the formation of hcp phase in metallic matrix. Meanwhile, the corrosion resistance of the coatings slightly reduced because cobalt is more active metal with respect to nickel.

Microstructural Characterization of Cermet Cladding Developed Through Microwave Irradiation

In the present work, cladding of hardfacing WC10Co2Ni powder on austenitic stainless steel has been developed through a novel processing technique. The clads were developed using microwave hybrid heating. The clad of average thickness ~2 mm has been developed through the exposure of microwave radiation at frequency 2.45 GHz and power 900 W for the duration of 360 s. The developed clads were characterized using field emission scanning electron microscope, X-ray elemental analysis, X-ray diffraction, and measurement of Vicker’s microhardness. The microstructure study of the clad showed good metallurgical bonding with substrate and revealed that clads are free from any visible interface cracking. Clads were formed with partial dilution of a thin layer of the substrate. The cermet microstructure mainly consists of relatively soft metallic matrix phase and uniformly distributed hard carbide phase with skeleton-like structure. The developed clads exhibit an average microhardness of 1064 ± 99 Hv. The porosity of developed clad has been significantly less at approximately 0.89%.

AlSi11/ Si<sub>3</sub>N<sub>4</sub> Interpenetrating Composites Tribology Properties of Aluminum Matris Composites

In present work, the metal-ceramic interpenetrating composites (IPCs) as AlSi11/ Si3N4 are fabricated by infiltrating technique. IPCs exhibit special characterization of brittle ceramic reinforced phase introduced by ductile metal matrix phase. During the sliding wear processes, IPCs exhibit four wear mechanism such as initial adhesive wear, mixed adhesive and abrasive wear, adhesive wear and final abrasive wear. Reinforcements inhibit plastic flow and restrict propagation of wear cracks. Increase in the volume fraction of reinforcement leads to improvement in the wear resistance. Under higher load and lower round speed conditions, the friction coefficients are lower than that of relative conditions.

Effect of SiCp as Reinforcement on the Corrosion Behavior of Cast Al-Mg Matrix

Metal matrix composite (MMC) are engineered materials manufactured by the action of incorporated reinforcement materials into metal matrix. As a result, stiff and hardened reinforcing phase in metallic matrix is obtained. The matrix includes a wider range of non-ferrous structures; meanwhile reinforcing phases comprise hardened nonmetallic particulates. The purpose of this paper is to investigate microstructural and electrochemical behavior of Al-Mg matrix reinforced with SiC particles (SiCp). The aluminum metal matrix composite was manufactured by the foundry vortex method. In the vortex process, SiC particles mixed into steel tubes at 1500 rpm were added to molten Al-Mg as-cast alloy. The metal-matrix composite (MMC) was characterized with the purpose of studying chemical interactions of SiC particles with the metal-matrix and its respective effect in electrochemical behavior. Results show that anodic dissolution in the cast Al-Mg matrix was accelerated by the formation of a non-stable oxide layer exhibiting partial protection with small resistance to polarization conditions, while the corrosion phenomena in Al-MMC was inhibited by the addition of silicon carbide particles

On the Influence of Carbon Nanotubes and Processing on Tensile Response and Fracture Behavior of a Magnesium Alloy

Carbon nanotube (CNT) reinforced magnesium alloy (AZ31)-based composite was fabricated using the technique of solidification processing followed by hot extrusion. In this paper is presented and briefly discussed the conjoint influence of reinforcement and processing on microstructural development, microhardness, tensile deformation and final fracture behavior of the magnesium alloy composite and comparisons made with the unreinforced alloy (AZ31). The interactive influences of the CNT reinforcement and processing in governing engineering stress versus engineering strain response and tensile properties is neatly presented and discussed. The macroscopic fracture mode and intrinsic microscopic mechanisms governing quasi-static deformation and fracture behavior of both the CNT reinforced and unreinforced magnesium alloy is both elaborated and rationalized in light of the specific role played by presence of reinforcing phase in the magnesium alloy metal matrix, intrinsic microstructural effects and nature of loading.

Ductility of bulk metallic glass composites: Microstructural effects

Recent experimental findings suggest that the problem of catastrophic failure by shear band propagation in monolithic bulk metallic glasses (BMGs) can be mitigated by forming two-phase composites consisting of a glassy metal matrix phase and a soft crystalline reinforcement phase. Here, we employ a recently introduced phase-field model in two spatial dimensions, capable of capturing shear banding in BMG systems, to address the effects of microstructure on the mechanical properties of BMG composites. We identify an important geometric length scale associated with the dendritic particles and demonstrate that it controls the overall ductility and ultimate strength of such BMG composites.

Friction and wear studies of die cast aluminum alloy‐aluminum oxide‐reinforced composites

PurposeMetal matrix composites (MMCs) are engineered materials formed by the combination of metal matrix and reinforcement materials. They have a stiff and hard reinforcing phase in metallic matrix. The matrix includes metals such as aluminum, magnesium, copper and their alloys. The purpose of this paper is to describe the development of an aluminum alloy‐aluminum oxide composite using a new combination of vortex method and pressure die casting technique and the subsequent tribological studies.Design/methodology/approachAn aluminum alloy‐aluminum oxide composite was developed using vortex method and pressure die casting technique. The aluminum alloy‐1 wt% aluminum oxide was die cast using LM24 aluminum alloy as the matrix material and aluminum oxide particles of average particle size of 16 μm as a reinforcement material. The friction and wear characteristics of the composite were assessed using a pin‐on‐disc set‐up; the test specimen, 8‐mm diameter cylindrical specimens of the composite, was mated against hardened En 36 steel disc of 65 HRC. The tests were conducted with normal loads of 9.8, 29.4 and 49 N and sliding speeds of 3, 4 and 5 m/s for a sliding distance of 5,000 m. The frictional load and the wear were measured at regular intervals of sliding distance.FindingsThe effects of normal load and sliding speed on tribological properties of the MMC pin on sliding with En 36 steel disc were evaluated. The wear rate increases with normal load and sliding speed. The specific wear rate marginally decreases with normal load. The coefficient of friction decreases with normal load and sliding speed. The wear and friction coefficient of the aluminum alloy‐aluminum oxide MMC are lower than the plain aluminum alloy. The wear and coefficient of friction of the entire specimens are lower.Practical implicationsThe development of aluminum alloy‐aluminum oxide composite using vortex method and pressure die casting technique will revolutionize the automobile and other industries, since a near net shape at low cost and very good mechanical properties are obtained.Originality/valueThere are few papers available on the development of (or tribological studies of) MMCs including aluminium/aluminium alloy‐ceramic composites developed by combination of vortex method and pressure die casting technique.

Synthesis and Characterization of Cu and Ni Bearing Nano-Composites and Nano-Structured Alloys

It is well recognized the importance of nano-structured materials in the present technological stage. Due to their unique properties these materials can be used in a large number of applications. One example is the growing interest in nanocomposites, in which a very fine dispersion of a ceramic phase in a metal matrix will significantly improve the material properties. In view of that, extensive studies have been carried out on a variety of materials such as alloys and different types of composites. Recently, the authors have developed a novel chemical method for in-situ formations of Cu-Al2O3 and Ni-Al2O3 nanoscale composites by decomposition of their mixed nitrate solutions, to co-form the nano oxides, followed by preferential reduction of CuO or NiO by hydrogen at very low temperature. Studies carried out by the authors on the kinetics of reduction of such fine oxides indicated that under low partial pressure of hydrogen (0.25 atm) in argon, the oxides of Ni and Cu can be reduced completely, in a low temperature range of 523 to 623 K. The composites containing nanosized metal-metal oxide particles have been found to be quite homogeneous in nature. In view of this, Cu-Ni and Ni-Co alloys was also produced by mixing the respective aqueous nitrate solutions, followed by decompositions of their nitrates to their mixed oxides and subsequent low temperature hydrogen reduction. In that context, the purpose of the present work is to address the fundamental aspects of the synthesis procedure, emphasizing the basic thermodynamics background of the two steps involved. Also, the work aims to illustrate the outcome, by presenting experimental conditions and providing relevant characterization of the obtained nano-materials, by means of electronic microscopy and X-Ray Diffraction. Examples are given in terms of the obtained nano-composites and alloys.

Effects of casting temperature on mechanical properties of Zr-based metallic glasses

The effects of casting temperature on microstructure and mechanical properties of as-cast 3mm-diameter Zr64.9Al7.9Ni10.7Cu16.5 and Zr47Cu37.5Ag7.5Al8 alloys were investigated. It was found that crystalline phases were precipitated in amorphous matrix as casting temperature increased. The compressive strength and Hv of as-cast Zr64.9Al7.9Ni10.7Cu16.5 and Zr47Cu37.5Ag7.5Al8 alloys increased slightly when casting temperature increased. However, ultrahigh casting temperature resulted in formation of hard crystalline phase in metallic glass matrix, which caused increase of hardness and density, but decrease of compressive strength.

In-Diffusion and Out-Diffusion of Oxygen from a Composite Containing Random Traps

In this paper, we investigate oxygen in-diffusion and out-diffusion with respect to a cermet composite where oxygen segregates at the interface between the metal matrix phase and the ceramic oxide phase. This phenomenological diffusion problem is treated by overlaying it with a fine-grained lattice that was addressed using a Lattice Monte Carlo method and a little-known exact expression for the lattice-based effective diffusivity in the presence of random traps. It is shown that there is very good agreement for the oxygen concentration depth profiles between the Monte Carlo results and the exact expression.

Fabrication and abrasive wear properties of metal matrix composites reinforced with three-dimensional network structure

Reticulated polyurethane was chosen as the preceramic material for preparing the porous preform using the replication process. The immersing and sintering processes were each performed twice for fabricating a high-porosity and super-strong skeleton. The aluminum magnesium matrix composites reinforced with three-dimensional network structure were prepared using the infiltration technique by pressure assisting and vacuum driving. Light interfacial reactions have played a profitable role in most of the ceramic-metal systems. The metal matrix composites interpenetrated with the ceramic phase have a higher wear resistance than the metal matrix phase. The volume fraction of ceramic reinforcement has a significant effect on the abrasive wear, and the wear rate can be decreased with the increase of the volume fraction of reinforcement.

Microstructure of Thin-Gauge Austenitic and Ferritic Stainless Steel Joints Brazed using Metglas® Amorphous Foil

Vastly different microstructures are formed in 304LN austenitic and Fecralloy® ferritic stainless steel joints brazed with Ni-15Cr-1.4B-7.25Si (MBF-51) and Ni-19Cr-1.5B-7.3Si (MBF-50), filler metals, respectively. These joints were cut from an industrial heat exchanger and a metallic catalyst support that were subjected to a short optimal brazing cycle in a vacuum furnace. A detailed description is given of the composition and morphology of phases evolved in these brazements, as a result of complex metallurgical reactions between the base and filler metals. A new metal- lurgical reaction was discovered between Fe-20Cr-5Al Fecralloy base metal (BM) having b.c.c. crystal lattice, and the Ni and B from MBF-50 (Ni-19Cr-1.5B-7.25Si) brazing filler metal (FM). This reaction resulted in the precipitation of fine, regularly distributed Nix (Al)y particles in the base metal matrix phase, thus strengthening Fecralloy braze- ments. The microstructure discovered in this work is remarkably similar to that of conventional precipitation-hard- ened, heat resistant alloys. Therefore, these joints can withstand years of service in the brutal environment observed in automotive exhaust pipes. IIW-Thesaurus keywords: Austenitic stainless steels; Stainless steels; Steels; Ferritic stainless steels; Microstructure; Brazed joints; Amorphous metals; Parent material; Brazing fillers; Filler materials; Gap; Joint preparation; Age hard- ening; Hardening; Heat treatment; Reference lists.

INFLUENCE OF REINFORCEMENT AND PROCESSING ON THE WEAR RESPONSE OF TWO MAGNESIUM ALLOYS

ABSTRACT Reinforcement of magnesium alloys with ceramic particulates has engineered a new family of materials that are marketed under the trade name metal-matrix composites. Rapid strides in the processing of these materials during the last two decades have provided the necessary impetus for their emergence and use in structure and automotive-related components. In this paper are reported the results of a study aimed at understanding the role of the reinforcing phase on the wear behavior of two magnesium alloys discontinuously reinforced with silicon carbide (SiC) particulates and saffil alumina short fibers. The wear rate of the reinforced magnesium alloy metal matrices is lower than that of the unreinforced counterpart (AM60-T5 and AZ92-T6). The improved wear resistance of the composite microstructures is attributed to the presence and distribution of the ceramic reinforcement phase, which minimizes the tendency for material flow or plasticity at the surface during sliding. Wear rate is influenced by sliding speed, nature, and volume fraction of the reinforcing phase. For the unreinforced magnesium alloys, an increase in sliding speed results in a marginal increase in wear rate. For a given reinforcement (particulate and saffil fiber) in the magnesium alloy metal matrix, an increase in sliding speed had a negligible influence on wear rate. An increase in volume fraction of the reinforcing phase in the magnesium alloy metal matrix resulted in a noticeable drop in wear rate. Coefficient of friction of the unreinforced magnesium alloys AM60 and AZ92 decreased with an increase in sliding speed regardless of the amount of applied load. Addition of reinforcement, i.e., particulates and short fibers, to the magnesium alloy metal matrix resulted in a significant drop in coefficient of friction. However, increase in volume fraction of the reinforcing base in the magnesium alloy metal matrix had negligible influence on coefficient of friction. The wear characteristics of the reinforced metal matrix are discussed in light of the mutually interactive influences of intrinsic microstructural effects, strength of the microstructure, sliding speed, and local stress state.

Microstructural characterization and wear behavior of laser cladded nickel-based and tungsten carbide composite coatings

Laser cladded nickel-based and tungsten carbide (WC) composite coatings were produced by varying laser beam power and were characterized by scanning electron microscopy. Microstructure of the clad layer is greatly affected by the processing parameters. The layer produced under the optimized processing conditions had uniform structure and excellent bonding with the substrate and was free of pores and cracks. Due to the right selection of the laser processing parameters, WC particulates partially dissolved, with the epitaxially grown dendrites around them, combined strongly with the coating materials and well-distributed in the layer. The larger the laser beam power is, the higher level of the dissolution of WC phase in metal matrix is, and the more WC particles tended to sink to the bottom of the layer. The wear test results show that the composite coating with WC hard phases has improved wear resistance when compared with the Ni-based alloy coating. The wear mechanism of the specimens is discussed based on microscopic observation of the worn surface and wear scraps.

Effect of Particulate Silicon Carbide on Cyclic Plastic Strain Response and Fracture Behavior of 6061 Aluminum Alloy Metal Matrix Composites

In this paper, the cyclic stress response and cyclic stress–strain response characteristics, cyclic strain resistance and low-cycle fatigue life, and mechanisms governing the deformation and fracture behavior of aluminum alloy 6061 discontinuously reinforced with silicon carbide (SiC) particulates are presented and discussed. Two different volume fractions of the carbide particulate reinforcement phase in the aluminum alloy metal matrix are considered. The composite specimens were cyclically deformed using fully reversed tension–compression loading under total strain-amplitude-control. The stress response characteristic was observed to vary with strain amplitude. The plastic strain-fatigue life response was found to degrade with an increase in carbide particulate content in the metal matrix. The fracture behavior of the composite is discussed in light of the interactive influences of composite microstructural effects, cyclic strain amplitude and concomitant response stress, deformation characteristics of the composite constituents and cyclic ductility.

Composite magnetostrictive materials for advanced automotive magnetomechanical sensors

In this paper we present the development of a composite magnetostrictive material for automotive applications. The material is based on cobalt ferrite, CoO⋅Fe2O3, and contains a small fraction of metallic matrix phase that serves both as a liquid-phase sintering aid during processing and enhances the mechanical properties over those of a simple sintered ferrite ceramic. In addition the metal matrix makes it possible to braze the material, making the assembly of a sensor relatively simple. The material exhibits good sensitivity and should have high corrosion resistance, while at the same time it is low in cost.

Structure of laser cladded tungsten carbide composite coatings

Carbide-metal matrix composite materials are used in applications were high wear resistance is critical. The laser surface cladding technique offers new advantages in depositing composite materials wear resistant coatings. Layers of WC in Co and Ni-based alloys matrix composites have been laser cladded on a low carbon steel substrate. Due to the right selection of the laser processing parameters during laser surface cladding porosity and crack free WC-metal composite coatings have been produced. The results of optical and SEM microstructure observations, X-ray phase, and EDS chemical composition analysis as well as cross-sectional microhardness distribution have been presented. The longer the laser beam–composite material interaction time, the higher level of the dissolution of primary carbide phase in metal matrix is to be expected. The primary WC particles dissolution degree depends also on their mesh size and volume fraction in composite material. The processing conditions should be optimized to keep the primary carbides dissolution at minimum.

Continuum analysis of dispersed-phase martensitic transformation toughening of two-phase metallic materials

Finite element analysis was used to study the martensitic transformation toughening in a two-phase metallic system consisting of a transforming metallic phase embedded in the form of small particles in a stable (non-transforming) metallic matrix phase. The material constitutive model for dispersed-phase transformation plasticity recently developed by Grujicic and Sankaran [1] was used for continuum description of the material behavior. Transient crack growth was simulated in the finite element mesh by a nodal release technique. The remote crack-opening tensile load was adjusted to mantain the near-tip energy release rate at the level necessary for crack advance. The transformation zone surrounding the crack tip and the resistance curves were computed for several levels of thermodynamic stability of the transforming phase. An optimum level of thermodynamic stability of the dispersed phase which gives rise to a maximum enhancement in material fracture toughness has been identified. Finally, the analysis was used to rationalize a nearly 100 percent increase in the fracture toughness observed by Grujicic and Dang [2] in a material system consisting of the gamma TiAl matrix and a 10vol.% of a Ti-Al-V-Fe beta phase dispersion.