Unreinforced Matrix Alloy Research Articles

Sliding Wear Behavior of TiC-Reinforced Cu-4 wt.% Ni Matrix Composites

The present investigation explores the effect of TiC content on the sliding wear properties of Cu-4 wt.% Ni matrix composites. Cu-4 wt.% Ni − x wt.% TiC (x = 0, 2, 4 and 8 wt.%) metal matrix composites were developed by powder metallurgy route. Their friction and wear was studied under dry sliding at different loads of 5, 7.5 and 10 N and constant sliding speed of 2 m/s using a pin-on-disk machine. The metallographic observations showed an almost uniform distribution of TiC particles in the matrix. Hardness of the composites increased with increasing TiC content (up to 4 wt.%). Friction and wear results of TiC-reinforced composites show better wear resistance than unreinforced matrix alloy. However, the optimum wear resistance was observed for 4 wt.% TiC-reinforced composites. Worn surfaces of specimens indicated the abrasion as the primary mechanism of wear in all the materials investigated in the study. The observed behavior has been explained on the basis of (1) the hardness which results in a decrease in real area of contact in composites containing TiC particles and (2) the formation of a transfer layer of wear debris on the surface of the composites which protects underlying substrate by inhibiting metal-metal contact.

Ageing Response of Powder Metallurgy AZ91 and AZ91 Reinforced with Multiwall Carbon Nanotube

Powder metallurgy metal matrix composites based on AZ91 alloy matrix reinforced with 0.3, 0.6 and 0.9 weight percent of multiwall carbon nanotube (MWCNT) were investigated from the point of view of their response to artificial ageing as compared to the unreinforced AZ91 matrix alloy. Mg-Zn-Al (AZ91) and its composite were prepared by milling the raw materials and followed by sintering at 450°C for 2 hours. The sintered samples were solution treated at 415°C for 2 hours and followed by artificial ageing at 175°C. The ageing behavior was monitored by following the phase analysis and hardness of the samples examined. Microstructure of the sintered composites indicated that MWCNT was embedded in the AZ91 matrix alloy. All composites indicated lower hardness than matrix, however AZ91reinforced with 0.6 and 0.9 weight percent of CNT showed accelerated ageing. X-ray diffraction pattern indicated the present of β-phase (Mg17Al12) that responsible for the hardening behavior.

High-temperature mechanical properties and fracture mechanisms of Al–Si piston alloy reinforced with in situ TiB2 particles

In order to assess the high-temperature performance of aluminum–silicon alloy reinforced with titanium diboride particles as potential piston material, the tensile behaviors and fracture mechanisms of in situ 4wt% TiB2/Al–Si composite were investigated in the temperature range 25–350°C. The tensile results revealed that the composite exhibited higher modulus than the matrix alloy at all testing temperatures, but both the matrix alloy and the composite presented similar strength levels above 200°C. The ductility of the composite was found to be lower than that of the unreinforced matrix alloy at 25 and 200°C, but no obvious distinction was observed at 350°C. The effects of temperature and the presence of TiB2 particles on tensile properties of the composite had been evaluated. Fractographic morphology studies were done using scanning electron microscope, which indicated that the fracture of the composite altered from brittle to ductile mode with temperature increasing. At 25 and 200°C, fracture was dominated by cracked silicon particles and separated TiB2 particles, while decohesion at particle–matrix interface was prevalent at 350°C. Analysis of the fracture surfaces also showed that regions of clustered TiB2 particles were found to be the locations prone to damage in the composite at both room and high temperatures.

Corrosion Behaviour of TiC-Reinforced Hadfield Manganese Austenitic Steel Matrix In-Situ Composites

The corrosion behaviour of Hadfield manganese austenitic steel matrix composite reinforced with the varying amount of TiC and unreinforced Hadfield manganese austenitic steel matrix alloy has been evaluated in 3.5% NaCl aqueous solution with the pH value of 6 by the potentiodynamic polarization curves and linear polarization resistance measurements at a scan rate of 1 mV/s at room temperature (25°C ± 2°C). The corrosion rate of the composites is higher than that of their unreinforced matrix alloy and it increases with the increasing volume fraction of TiC. The poor corrosion resistance of the composites can be attributed to the galvanic effects between the matrix and reinforcement.

Microstructure and mechanical properties of TiB2/2219 composites

In this work, the in situ TiB2 particulates reinforced 2219 aluminium matrix composites were fabricated using the mixed salts method. The microstructural characteristics and mechanical properties of TiB2/2219 Al composites were investigated. The reults show that the composites reinforced with 5 and 10 wt-%TiB2 exhibit higher Young’s modulus, yield strength and ultimate tensile strength than the unreinforced matrix alloy. The improvement in strength may be attributed to strengthen mechanisms including dislocation strengthening due to the CTE difference between the matrix alloy and TiB2 particulates, Orowan strengthening and load transfer.

Fatigue and Fracture Behavior of MMC in the HCF- and VHCF-Regime

Aluminum matrix composites (AMCs) are characterized by improved mechanical properties in comparison to their unreinforced matrix alloys. But the knowledge about the fatigue behavior of AMCs in the HCF-and in the VHCF-regime is limited until now. Due to this AMC225xe and AMC xfine225 with an average SiC particle content of 25 vol.-% and particle sizes of 2.5 μm and 0.7 μm, respectively, as well as the base alloy AA2124 were fatigued up to 1010 cycles using the ultrasonic testing facility of the type "UltraFast-WKK-Kaiserslautern".To describe the fatigue behavior of the specimens several measuring devices were used to monitor and record the central process parameters. A very sensitive value to detect specimen failure at an early stage is the dissipated energy which can be determined as the integral of the generator power depending on the ultrasonic pulse time.In comparison to AA2124 the investigated AMCs have shown a considerably enhanced fatigue performance for stress amplitudes higher than 140 MPa. But below this stress amplitude for the matrix alloy run outs at 1010 cycles were realized whereas the AMCs failed at lower number of cycles still at lower stress amplitudes. Moreover, while crack initiation of the matrix alloy in all cases started at the surface for the AMCs the crack initiation point changes from surface to subsurface for more than 107 cycles. The subsurface failures of the composites were caused by microstructural inhomogeneities which could be identified with EDX and micro-CT as particle clusters and copper-iron-rich inclusions.

Tensile behaviour and microstructure of magnesium AM60-based hybrid composite containing Al2O3 fibres and particles

Magnesium AM60 based metal matrix composites (MMCs) reinforced with alumina (Al2O3) fibre and/or particles were successfully fabricated by a perform-squeeze casting technique under an applied pressure of 90MPa. Tensile properties of unreinforced AM60 alloy, Al2O3 fibre/AM60 alloy metal matrix composite, and hybrid composite containing both Al2O3 fibres and particles were evaluated at the ambient temperature. The addition of fibres and particles significantly improved the tensile properties, but with a reduction in ductility in comparison to the unreinforced matrix alloy. The observation of SEM fractographs indicates that the fracture mode of the composites is the evolution of localized damages, such as particles and fibres damage and cracking, matrix fracture, and interface debonding, which are consistent with the tensile results.

Effect of the Sic Particle Orientation Anisotropy on the Tensile Properties of a Spray-Formed Sicp/Al-Si Composite

The effects of the SiC particle orientation anisotropy on the tensile properties of spray-formed SiCp/Al-Si composites was investigated and compared with that of the unreinforced matrix alloy. The addition of SiC particles increased the elastic modulus but decreased ultimate tensile strength and elongation of an Al–Si alloy under peak-aged conditions. Microstructure disolayed a preferred orientation of the reinforcement particles, which were inclined to align parallel to the extrusion axis. Meanwhile, the degree of orientation anisotropy turned to be higher with larger reinforcement sizes particle. The elastic modulus, tensile strength and elongation in the longitudinal orientation (parallel to the extrusion axis) were higher than those in the transverse orientation (perpendicular to the extrusion axis). The fracture mechanism in a composite with 4.5 μm particles was attributed to interfacial debonding between SiC and matrix in the two orientations. However, in case of aluminum reinforced wild 20 μm particles, both cracking of SiC particles in the longitudinal orientation and the interfacial debonding in the transverse orientation played an important role in fracture.

Effects of trace TiB and TiC on microstructure and tensile properties of β titanium alloy

In the present work, a β titanium alloy reinforced by trace TiB whiskers and TiC particles was fabricated by common casting and hot-forging. For comparative study, the unreinforced titanium matrix alloy was also fabricated by the same casting and forging process. The microstructure, room temperature, tensile properties and fracture characteristics of the composite and the matrix alloy are presented and discussed. Microstructural analysis of the composite revealed that the reinforcements were uniformly dispersed after forging. The size of the β grains in the composite was refined after solution treatment under the β field. The secondary α lath was also refined during aging heat treatment by the addition of trace boron and carbon. The results of the tensile tests show that the improvement in the strength of the composite can be attributed to the refinement in the grain size and the secondary α lath, while the remarkable reduction in the ductility can be ascribed to the cracking of the reinforcements and the decohesion at the interface between the reinforcements and the matrix.

Effect of Forging Parameters on Low Cycle Fatigue Behaviour of Al/Basalt Short Fiber Metal Matrix Composites

This paper deals with metal matrix composites (MMCs) of Al 7075 alloy containing different weight percentage (2.5, 5, 7.5, and 10) basalt short fiber reinforcement and unreinforced matrix alloy. The samples were produced by the permanent stir casting technique. The casting ingots were cut into blanks to be forged in single stage and double stage, using MN press and graphite-based lubricant. The microstructures and fatigue properties of the matrix alloy and MMC samples were investigated in the as cast state and in the single and double stage forging operations. The microstructure results showed that the forged sample had a uniform distribution of the basalt short fiber throughout the specimens. Evaluation of the fatigue properties showed that the forged samples had higher values than those of the as cast counterparts. After forging, the enhancement of the fatigue strength of the matrix alloy was so significant and high in the case of 2.5 and 5.0 wt. percentage basalt short fiber reinforced MMC, and there was no enhancement in 7.5 and 10 weight percentages short fiber reinforced MMCs. The fracture damage was mainly due to decohesion at the matrix-fiber interface.

Surface Integrity of High Speed Milling of Al/SiC/65p Aluminum Matrix Composites

The surface quality of components produced through milling of particle reinforced aluminum matrix composites (PRAMCs) is one of the most important factors influencing their practical performance. Therefore, the increasing applications of PRAMCs necessitate an in-depth understanding of the variation law of surface integrity. This paper presents a systematic experimental research of high speed milling of Al/SiC/65p (65% volume fraction) by polycrystalline diamond tools (PCD). The influences of cutting parameters on surface roughness (Ra), surface residual stress (RS) and morphology of PRAMCs were investigated. In addition, the experiments on corresponding unreinforced matrix alloy Al 6063 were also carried out to analyze the influence of the present reinforcements on surface integrity. The results of full factorial experiment revealed that the most significant milling parameter for surface roughness was milling speed, followed by the interaction between feed rate and milling speed, then the feed rate. In terms of residual stress on the machined surface, axial depth of cut had the highest influences on surface residual stress, followed by milling speed and feed rate. The results of single-factor experiment demonstrated that surface roughness improved slightly with the decrease in the feed rate, while the effect of milling speed was negligible. Residual stress measured in feed direction by X-ray diffraction (XRD) indicated that the conditions of machined Al6063 surface were all tensile, while the conditions of Al/SiC/65p were compressive.

Bending Properties of AA7055 Aluminum Alloy Reinforced with <i>In Situ</i> TiB<sub>2</sub> Particles

In-situ TiB2 particles reinforced AA7055 composites were fabricated through mixed-salts route and their bending properties were studied. The composites reinforced with 5 wt % and 10 wt% TiB2 exhibit higher bending strength than the unreinforced matrix alloy. The improvement in bending strength may be attributed to dislocation strengthening, Orowan strengthening, and grain strengthening. The good bonding between the reinforcements and the matrix also plays an important role.

Effect of Fiber Volume Fraction on High Temperature Creep of Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub>(sf)/AZ91D Composite

Constant stress tensile creep tests were conducted on AZ91D–20 vol.%, 25 vol.%, and 30 vol.% Al2O3-SiO2short fiber composites and on an unreinforced AZ91D matrix alloy. The creep resistance of the reinforced materials is shown to be considerably improved compared with the matrix alloy. With the increasing volume fraction of short fibers, the creep resistance of AZ91D composites is improved, and their creep threshold stresses are also increased accordingly. Because of the increasing volume fraction of short fibers, loads of bearing and transmission of short fibers will increase, and thus the creep resistance of AZ91D composites further improves, but the precipitation of β-Mg17Al12precipitate increases in the number, it is easy to soften coarse, so that threshold stress of AZ91D composite does not increase greatly.

Numerical simulation on tensile property of TiC particle reinforced titanium matrix composite

Samples of TiC particle reinforced titanium matrix composite (TP‐650) containing 10 vol.‐% of TiC fabricated by pretreatment melt process have been tested in quasi‐static and dynamic tension at different strain rates from 10−4 to 103 s−1, and the mechanical properties have been compared with those of the unreinforced matrix alloy. homogenization theories for periodic microstructures and the fixed point iteration method for multiparticle unit cell’s boundary conditions are introduced to investigate the mechanical characteristics of the TiC reinforced titanium matrix composites (TP‐650). Finite element models containing some microstructure characteristics of the TP‐650 composites are established. The relationship between the mechanical behaviours and the microstructure parameters was studied.

Mechanical and microstructural properties of TiC particle-reinforced titanium matrix composite

Samples TiC particle (TiCp) reinforced titanium matrix composite containing 10 vol pct of TiC fabricated by pre-treatment melt process (PTMP) have been tested in quasi-static and dynamic tension at different strain rates from 10 –4 to 10 3 /s, and the mechanical properties have been compared with those of the unreinforced titanium matrix alloy. It has been found that under dynamic loadings, both the titanium matrix alloy and the TiCp/Ti composite demonstrate some strain-rate sensitivity. The tensile strength and the fracture strain increase with increasing strain rate. The damage mechanisms are different for the titanium matrix alloy and the TiCp/Ti composite, as demonstrated by the scanning electron microscopy (SEM) observation of fracture surfaces for both the matrix and the composite. The tensile-tested titanium matrix alloy shows dimpled fracture, while the tensile-tested TiCp/Ti composite exhibits cleavage failure followed by the ductile fracture of the titanium matrix alloy.

EVALUATION OF PITTING CORROSION OF THE SiCP/5A06 ALUMINUM METAL COMPOSITE IN 3.5% NaCl SOLUTION BY MEANS OF ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY (EIS)

The corrosion behavior of the silicon carbide particulates (17.5 vol.%) reinforced 5A06 aluminum alloy metal matrix composite (MMC) and the 5A06 aluminum matrix alloy has been studied in 3.5% NaCl solution at 35°C by using electrochemical impedance spectroscopy (EIS). Analysis of the results, which were obtained from optical (OM) and scanning electron microscopy (SEM) attached with energy dispersion spectroscopy (EDS), indicate that the corrosion behavior of the materials studied was mainly localized corrosion due to the presence of intermetallics ( Al ( Mn , Fe ), Al ( Si , Mg )) on the surface and crevices at the interface of SiCp/matrix . More numerous, wider spread, smaller and shallower pits were noted on the composite surface relative to the unreinforced matrix alloy during immersion. However, the pitting morphology on both materials was completely different from crystallographic type of pitting. Crystallographic pitting occurred by anodically polarizing the materials above the pitting potential. Further, the occurrence of an inductive time constant at lower frequencies region and the lower impedance as compared to that of the matrix alloy indicate that the corrosion extent of the composite was more severe than that of the matrix alloy, both materials were immersed for varied periods. Two different equivalent circuits were proposed and applied to analyze the EIS measurements, which can simulate the impedance of the composite and the matrix alloy under corrosive environment.

Wear-Resistant Property of SiCp/Al Composites

Al alloy reinforced with SiCp (size: 70-220μm) was fabricated by pressureless-infiltration. Its wear resistant property was investigated under different heat-treatment conditions, and morphology of worn surface was examined. The results showed that the composite was integrated, uniform and compact, and its wear resistant property was better than that of the unreinforced matrix alloy. It was indicated that some rigid SiCp in the abraded surface of the composite could support part of loads and replace matrix to wear-tear, which improved the wear resistant property. Compared to annealing, solution aging strengthens Al alloy matrix and cohesion with SiCp, and the wear resistant property of composites was better. Combining interface is also an important factor which influences on wear resistant property. During the wear test, the smaller SiCp size, the more interfaces, there are more SiCp falling off because of loosening combining interface, which results in more wear-tearing value. The wear rate of composite increases with decreasing SiCp size, thus, the composite with larger SiCp has better wear-resistant property than that with smaller SiCp. At last, the wear mechanism of the composite was also studied, and it showed that abrasive wear dominated in the abrasion process.

Production of A1 Based Composite Reinforced with SnO2 Coated SiC Particles

An investigation was carried out on SnO2 coating of SiC particles by sol-gel technique and the production of SnO2 coated 20 vol% SiC particle reinforced composite and unreinforced matrix alloy by squeeze casting. The morphology of the coating and microstructural, interfacial and mechanical properties of the composite were characterized by using an optical microscope, image analyzer, scanning electron microscope (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD). It has been found that the coating is not degraded during the fabrication process; in other words, SnO 2 coating by sol-gel technique is an effective way to improve the matrix/reinforcement interfacial properties.

Effect of interfacial bonding on uniaxial ratchetting of SiC P/6061Al composites: Finite element analysis with 2-D and 3-D unit cells

The effect of interfacial bonding state between particulate and metal matrix on the ratchetting of SiC particulate reinforced 6061Al alloy composites (i.e., SiC P/6061Al composites) in uniaxial cyclic stressing at room temperature was discussed by numerical simulation using a finite element code ABAQUS. In simulation, axi-symmetrical two-dimensional (i.e., 2-D) mono-particle and three-dimensional (i.e., 3-D) multi-particle unit cells were employed, respectively. The ratchetting of un-reinforced matrix alloy was addressed by an elasto-plastic constitutive model with nonlinear kinematic hardening rule, and the particulates were assumed as elastic. Two kinds of interfacial layers were inserted into the unit cells between particulate and matrix, i.e., elastic and elasto-plastic interfacial layers previously employed by Kang et al. [G.Z. Kang, Q. Gao, Composites A 33 (2002) 657–667] in the numerical simulation for monotonic tensile behavior of short fiber reinforced metal matrix composites. Finally, the ratchetting of T6-treated SiC p/6061Al composites was simulated by using 3-D multi-particle unit cell and suitable interfacial property parameters. It is shown that the simulated results are closer to the corresponding experiments than those obtained with assumption of perfect interface. Simultaneously, some microscopic deformation features in the composites and their evolution rules were also revealed by the numerical simulation. Some significant conclusions are obtained, which are useful to establish a constitutive model to describe the ratchetting of the composites.

The sliding wear behavior of TiCp/AZ91 magnesium matrix composites

The AZ91 metal matrix composites (MMCs) reinforced with 5, 10 and 15 wt.% TiC particulates are fabricated by TiCp–Al master alloy process combined with mechanical stirring. The effects of TiC particulate content, applied load and wearing time on the sliding wear behaviors of the composites were investigated using MM-200 wear testing apparatus. The results show that the wear resistance and friction coefficient of the composites increased and decreased with increase of the TiC particulate content, respectively. The wear volume loss and friction coefficient of the reinforced composites as well as the unreinforced AZ91 matrix alloy increased with increase of applied load or wearing time, but the increase rates of the reinforced composites in two performance is lower than those of the unreinforced AZ91 matrix alloy. Furthermore, the sliding wear behavior of the composites and the unreinforced AZ91 matrix alloy is characterized by ploughing, adhesion and oxidation abrasion.