Various TEM methods for the study of metal matrix composites

We have investigated the applicability of a number of TEM techniques for the study of the metal/ceramic interface in a short fibre metal matrix composite (SFMMC). In particular, we found that dark field techniques were best suited to the study of any possible (0.4-2 nm) amorphous layer. High resolution imaging was found to be difficult to use because of the absence of well defined ‘edge-on’ interfaces, but EELS with parallel recording was found to be very useful for finding and identifying segregated particles at the fibre/matrix interface. It was also shown that micro-mechanisms of fracture such as voiding and fibre breakage could be readily examined by TEM using a foil preparation method which resulted in an ‘edge-on’ fracture surface and an observation region extending about 0.8 mm below it.     

Dry three-body abrasive wear behavior of WC reinforced iron matrix surface composites produced by V-EPC infiltration casting process

This paper fabricated tungsten carbide (WC) particles reinforced iron matrix surface composites on gray cast iron substrate using vacuum evaporative pattern casting (V-EPC) infiltration process, investigated dry three-body abrasive wear resistance of the composites containing different volume fractions of WC particles, comparing with a high chromium cast iron. The fabricated composites contained WC particles of 5, 10, 19, 27, 36, and 52 vol.%, respectively. The results in abrasive wear tests showed that, with the increase in the volume fraction of WC particles, the wear resistance of the composites first increased until reached the maximum when the volume fraction of WC was 27%, then decreased, and was 1.5–5.2 times higher than that of the high chromium cast iron. The changes of the wear resistance of the composites with the volume fraction of WC particles and the mode of material removal in dry three-body abrasive wear condition were analyzed.     

Review of machining metal matrix composites

Monotonic fault progression is an important assumption for a number of prognostic models. This assumption can be violated through human intervention and self‐healing and result in non-monotonic degradation data which not only increases the uncertainty but also may cause model failure. Methods to analyze and handle non-monotonic degradation in repairable systems are practically nonexistent in the literature. In this research, we intend to consider repairable systems in which self‐healing is possible and human interventions are desirable. We presented a novel example of self-healing for fatigue cracks analyzed by acoustic emission. The aim of the present paper is to initiate a new research area on using non-monotonic measures in degradation-based prognostics. However, this research is not a review of trend analysis techniques, and therefore, there are more techniques to be considered or developed in future studies. In effect, trend analysis should be considered as an integral part of prognostics and health management. This study considers trend analysis for three classes of data, (1) prognostic parameters, (2) degradation waveform, and (3) multivariate data. A new form of crest factor is introduced for more effective waveform analysis of non-monotonic data. In addition, two algorithms are introduced to treat non-monotonic trend. The prognostic model used in this research does not produce results without treating non-monotonicity. These kinds of algorithm have promising potential to treat non-monotonicity and deal with arbitrary stationary noise in degradation data.     

Tribological behavior of metal matrix composites

The wear and friction behavior of continuous graphite fiber reinforced metal matrix composites was investigated. Composite materials were tested against 4620 steel at 54 m s^?1 at room temperature in air without lubricant. The graphite fibers studied included rayon-, pitch- and polyacrilonitrile (PAN)-based fibers. Both high modulus and high strength PAN-based fibers were examined. The fibers were incorporated into copper- and silver-based alloys by means of a liquid metal infiltration technique. The results of this study indicate that the type of graphite fiber in the composite is the most significant factor in the wear and friction behavior of metal matrix composites. In some high modulus fiber tin-bronze composites the fiber fraction influences the wear rate but not the coefficient of friction. Neither the matrix alloy nor the composite tensile strength per se correlate with the friction and wear properties; however, there are specific trends for the various matrix alloys.     

Multi-response optimization of machining parameters on red mud-based aluminum metal matrix composites in turning process

This paper presents the findings of an experimental investigation into the effects of cutting speed, feed rate, depth of cut, and nose radius in computer numerical control (CNC) turning operation performed on red mud-based aluminum metal matrix composites. This paper investigates optimization design of a turning process performed on red mud-based aluminum metal matrix composites. The major performance characteristics selected to evaluate the process are surface roughness, power consumption, and vibration, and the corresponding turning parameters are cutting speed, feed, depth of cut, and nose radius. Taguchi-based grey analysis, which uses grey relational grade as performance index, is specifically adopted to determine the optimal combination of turning parameters. The principal component analysis (PCA) is applied to evaluate the weighting values corresponding to various performance characteristics. L9 orthogonal array design has been used for conducting the experiments. The outcome of confirmation experiments reveals that grey relational analysis coupled with PCA can effectively be used to obtain the optimal combination of turning parameters. Hence, this confirms that the proposed approach in this study can be a useful tool to improve the turning performance of red mud-based aluminum metal matrix composites in CNC turning process.     

Nano-additive manufacturing of multilevel strengthened aluminum matrix composites

Nanostructured materials are being actively developed, while it remains an open question how to rapidly scale them up to bulk engineering materials for broad industrial applications. This study propose an industrial approach to rapidly fabricate high-strength large-size nanostructured metal matrix composites and attempts to investigate and optimize the deposition process and strengthening mechanism. Here, advanced nanocrystalline aluminum matrix composites(nanoAMCs) were assembled for the first ...     

Aluminium–aluminium nitride composites fabricated by melt infiltration under pressure

Aluminium–matrix composites containing ~55 vol.% AlN particles were fabricated by melt infiltration of aluminium into an AlN preform under a pressure of up to 130 MPa. Two different AlN powders (H.C. Starck, Goslar, Germany, and ESK, Elektroschmelzwerk, Kempten, Germany) and four types of aluminium alloy (2024, 1070, 6060 and 5754) were used. The initial AlN powders were characterized by scanning electron microscopy. The composites were studied by light microscopy, scanning and transmission electron microscopies and energy-dispersive X-ray spectroscopy. Particle–matrix interfaces were observed using high-resolution electron microscopy. As a result of the melt infiltration process, the composites are very dense and the microstructure shows a homogeneous distribution of the reinforcement. The interfaces are clean with very little porosity. Some Al₂Cu precipitates were observed in the 2024 matrix.     

Research on interlayer remelting process of multi-layer forming by metal fused-coating additive manufacturing

Journal of Mechanical Science and Technology - In order to achieve good interlayer metallurgical bonding in the metal fused-coating additive manufacturing, the finite element thermal analysis model...     

颗粒增强金属基复合材料的制备进展

介绍颗粒增强金属基复合材料的常用制备工艺,分析各种制备方法的优缺点;论述对颗粒增强金属基复合材料制备技术研究的难点,并展望金属基复合材料的发展。     

金属基复合材料及其发展现状

综述了当前国内外金属基复合材料的发展现状、性能特点、应用及制备方法。     

Selection of optimal process parameters in WEDM while machining Al7075/SiCp metal matrix composites

Aluminium metal matrix composites (MMCs) reinforced with silicon carbide particulate (SiCp) find several applications due to their improved mechanical properties over the conventional metals for a wide variety of aerospace and automotive applications. However, the presence of discontinuously distributed hard ceramic in the MMCs made them as difficult-to-cut materials for conventional machining methods. The wire electrical discharge machining (WEDM), as a widely adopted non-traditional machining method for difficult-to-cut precision components, found an appropriate metal removal process for MMCs to enhance quality of cut within the stipulated cost. While machining the advanced materials like MMCs, a clear understanding into the machining performance of the process for its control variables could make the process uncomplicated and economical. In light of the growing industrial need of making high performance-low cost components, the investigation aimed to explore the machining performance characteristics of SiCp reinforced Al7075 matrix composites (Al7075/SiCp) during WEDM. While conducting the machining experiments, surface roughness, metal removal rate, and wire wear ratio are considered the responses to evaluate the WEDM performance. Response surface methodology is used to develop the empirical models for these WEDM responses. SiC particulate size and volume percentages are considered the process variables along with pulse-on time, pulse-off time, and wire tension. Analysis of variance (ANOVA) is used to check the adequacy of the developed models. Since the machining responses are conflicting in nature, the problem is formulated as a multi-objective optimization problem and is solved using the Non-dominated Sorting Genetic Algorithm-II to obtain the set of Pareto-optimal solutions. The derived optimal process responses are confirmed by the experimental validation tests, and the results are analyzed by SEM.     

Ductile damage micromodeling by particles’ debonding in metal matrix composites

The elastic–plastic behaviour of particle-reinforced metal matrix composites undergoing ductile damage is modelled using a two-level micro-structural approach. The considered heterogeneous material is a polycrystal containing intra-crystalline elastic particles. Ductile damage is initiated by the matrix/particle interface debonding and the subsequent voids growth with plastic straining of the crystalline matrix. Homogenization techniques are used twice: first at mesoscale to derive the equivalent grain behaviour and then to obtain the macroscopic behaviour of the material. Plastic deformation of the crystalline matrix is due to crystallographic gliding on geometrically well-defined slip systems. The associative plastic flow rule and the hardening law are described on the slip system level. The evolution of micro-voids volume fraction is related to the plastic strain. The elastic–plastic stress–strain response of particle composite is investigated. Predictions of the proposed model are compared to experimental data to illustrate the capability of the suggested method to represent material behaviour. Furthermore, specific aspects such as the stress triaxiality and yield surfaces are discussed.     

An investigation on manufacturing process parameters of CNG pressure vessels

Mass production of CNG pressure vessels requires an accurate understanding of process effective parameters. In this paper, the finite-element method has been used to study the vessel manufacturing parameters. The FE model has been verified by experimental results. The entire manufacturing process, including deep drawing, redrawing and ironing, of an aluminum liner sample of CNG pressure vessels (without spinning) have been simulated. The deep drawing process has been modeled by using three types of dies: flat, conical and tractrix; then drawing force and wall thickness variations have been compared. In order to achieve the final diameter of the liner, the redrawing process has been implemented in a conical die. To obtain a uniform wall thickness, the ironing process has been simulated in two stages, and the required force and die angle for each process have been extracted. The result of this work presents an integrated perspective for decision-making on the manufacturing of CNG liners.     

Spray forming of Al/SiC metal matrix composites

This paper describes the as-sprayed microstructure of a model Al-4wt%Cu/SiC particulate (Al4Cu/SiC_p) metal matrix composite (MMC) manufactured by spray forming, and the relationship between microstructure and solidification conditions during manufacture. Injection of SiC_p into the melt atomization region during the spray forming of Al4Cu results in significant SiC_p incorporation into molten droplets during atomization, and relatively little incorporation during flight to the substrate and at deposition. SiC_p clustering is evident in the Al4Cu droplets and results in clustering in the as-sprayed MMC deposit. Matrix dislocation and precipitation microstructures are dependent upon local solidification conditions during spray forming. Increased dislocation density and increased quantity of fine-scale θ′-Al₂Cu precipitation is found in the α-Al(Cu) matrix where local deposit cooling rates are high, i.e. in the vicinity of the substrate/deposit interface and when increased spray distances are used in manufacture. Lower dislocation density and increased quantity of grain-boundary θ-Al₂Cu is found where deposit cooling rates are relatively low, i.e. distant from the substrate/deposit interface and at decreased spray distances. In all cases, dislocation densities are higher in α-Al(Cu)/SiC_p interfacial regions than in the α-Al(Cu) matrix. There is no evidence of α-Al(Cu)/SiC_p interfacial reaction in the as-sprayed condition indicating that cooling rates during spray forming are sufficiently rapid to prevent reaction.     

The effect of microstructure and wear conditions on the wear resistance of steel metal matrix composites fabricated with PTA alloying technique

The concept of hard particles in a softer metal matrix has long appealed to number of industries dealing among others with drilling and mining. For these facilities, the PTA (Plasma Transferred Arc) alloying technique is advisable and advantageous for several reasons; the equipment may be portable and moved near the working site, the treatment may be applied strictly to the area where the wear problem is situated and after the treatment little machining is required. Four different coatings are tested against three different modes of wear occurring either alone or less frequently combined in this kind of applications, i.e. adhesion, low stress abrasion and two-body abrasion. Two of the coatings examined belong to the category of tool steels with very hard carbides in their microstructure, namely TiC, M₂C and M₆C. The other two are boride coatings belonging to the Fe–B and Fe–Cr–B system respectively. A heat treated AISI D2 tool steel commonly used in this type of applications is also examined for comparison. Fe–Cr–B coating performance is at least 2 times better in low stress and two-body abrasion and four orders of magnitude better in adhesion wear than the AISI D2 tool steel. Fe–B coating can be used in pure adhesion or abrasion situations, but their brittleness forbids their use in situations involving impact loading. AISI M2 coating presents similar wear performance with AISI D2 tool steel in abrasion, whereas in adhesion wear it performs at least two orders of magnitude better. MMC–TiC coating has good performance in pure two-body abrasion situations due to the presence of the very hard TiC particles in its microstructure.     

An investigation on the machinability of Al-SiC metal matrix composites using pcd inserts

The paper attempts to study the machinability issues of aluminium-silicon carbide (Al-SiC) metal matrix composites (MMC) in turning using different grades of poly crystalline diamond (PCD) inserts. Al-SiC composite containing 15%wt of SiC was used as work material for turning and PCD inserts of three different grades were used as cutting tools. Experiments were conducted at various cutting speeds, feeds and depth of cuts and parameters, such as surface roughness, specific power consumed, and material removal rate were measured. The worn surface of the insert was examined by scanning electron microscope (SEM). The surface finish observed was found to be much lower than the theoretical surface roughness. The influence of cut was examined for the different grades of PCD inserts. It was observed that the 1600 grade PCD inserts performed well from the surface finish and specific power consumption points of view closely followed by the 1500 grade.     

A study on the effect of interelectrode gap in the electrochemical additive manufacturing process

Electrochemical additive manufacturing (ECAM) is achieved by localized electrochemical deposition (LECD). The ECAM can print metal parts directly from computer models at macro-, micro- and nanoscales at room temperature without any thermal defects. This study aims to (1) simulate the effects of the interelectrode gap (IEG) on cation concentration and current density in the deposition zone during ECAM; (2) quantify the localization of the desired deposit, as well as unintended plating when using various IEGs, and (3) determine the rate of deposition for different IEGs. Current density patterns under stationary and moving anode conditions were analyzed to calculate deposition rate and the corresponding time to fill an IEG. Experiments were performed to monitor current density and time to fill IEG during deposition and compared with the simulation results. Studying the migration behavior of cations and the current density allowed deposition height to be predicted and the extent of plating to be quantified, using a distortion factor. It was found that for the ECAM conditions used in this study, smaller IEGs (<10?µm) result in lower rates of deposition due to the cation depletion, while larger IEGs (50?µm) result in an increase in plating tendency due to cation migration.