Showing papers on "Metal matrix composite published in 2014"

Study on mechanical and wear properties of Al 7075/Al2O3/graphite hybrid composites

Abstract: This work investigated the influence of graphite on the wear behavior of Al 7075/Al 2 O 3 /5 wt.% graphite hybrid composite. The investigation reveals the effectiveness of incorporation of graphite in the composite for gaining wear reduction. The Al 7075 (aluminium alloy 7075) reinforced with Al 2 O 3 –graphite were investigated. The composites were fabricated using liquid metallurgy route. Ceramic particles along with solid lubricating materials were incorporated into aluminium alloy matrix to accomplish reduction in both wear resistance and coefficient of friction. The Al 7075/Al 2 O 3 /graphite hybrid composite was prepared with 5 wt.% graphite particles addition and 2, 4, 6 and 8 wt.% of Al 2 O 3 . The hardness, tensile strength, flexural strength and compression strength of the Al 7075–Al 2 O 3 –graphite hybrid composites are found to be increased by increased weight percentage of ceramic phase. The wear properties of the hybrid composites containing graphite exhibited the superior wear-resistance properties.

A review of the electrodeposition of metal matrix composite coatings by inclusion of particles in a metal layer: an established and diversifying technology

Abstract: Following a brief overview of their history, which dates back to the 1920s with marked developments during the 1960s and 1970s, the principles of composite coatings, achieved by including particles dispersed in a bath into a growing electrodeposited metal layer, are considered. The principles and role of electroplating compared to other techniques for realising such coatings, are considered. A good quality particle dispersion (often aided by a suitable type and concentration of surfactants) appropriate choice of work-piece shape/geometry and controlled agitation in the bath are seen to be prerequisites for achieving uniform coatings having a well-dispersed particle content by electroplating. Examples are provided to illustrate the influence of bath composition and plating conditions on deposit properties. Engineering applications of included particle composite layers are illustrated by examples of hard ceramic, soft ceramic and polymer inclusion composite coatings from the recent literature. Current trends in the development of composite plated coatings are summarised and their diverse applications are seen to include the use of finely structured (especially nanostructured) and functionally active particles together with hybrid and more complex, e.g. hierarchical, structures for applications ranging from tribology to speciality electronics, magnetic and electrochemical energy conversion materials.

Laser cladding in-situ NbC particle reinforced Fe-based composite coatings with rare earth oxide addition

Abstract: Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance and high temperature properties. The effects of RE on the microstructure and properties of laser coatings have also got more and more attention. In this paper, in situ Fe-NbC composite coatings with different CeO2 addition were produced on die steel by laser cladding. The formation mechanism of NbC particles was analyzed. The effects of RE on microstructure and micro-hardness of coatings were investigated. It was revealed that larger NbC particles with hard edges formed around Nb particles, and smaller flocculent NbC particles formed by the chemical reaction of Nb and solid graphite in the molten pool. CeO2 plays important roles in reducing micro-porosities, refining grains, and improving the precipitation of NbC. Therefore, the average micro-hardness and its smoothness from the top to the bottom of the coating were improved after adding CeO2.

Properties of ceramic-reinforced aluminium matrix composites - a review

Abstract: A review of various properties of ceramic-reinforced aluminium matrix composites is presented in this paper. The properties discussed include microstructural, optical, physical and mechanical behaviour of ceramic-reinforced aluminium matrix composites and effects of reinforcement fraction, particle size, heat treatment and extrusion process on these properties. The results obtained by many researchers indicated the uniform distribution of reinforced particles with localized agglomeration at some places, when the metal matrix composite was processed through stir casting method. The density, hardness, compressive strength and toughness increased with increasing reinforcement fraction; however, these properties may reduce in the presence of porosity in the composite material. The particle size of reinforcements affected the hardness adversely. Tensile strength and flexural strength were observed to be increased up to a certain reinforcement fraction in the composites, beyond which these were reduced. The mechanical properties of the composite materials were improved by either thermal treatment or extrusion process. Initiation and growth of fine microcracks leading to macroscopic failure, ductile failure of the aluminium matrix, combination of particle fracture and particle pull-out, overload failure under tension and brittle fracture were the failure mode and mechanisms, as observed by previous researchers, during fractography analysis of tensile specimens of ceramic-reinforced aluminium matrix composites.

Analysis of Tribological Behavior of Aluminium/B4C Composite Under Dry Sliding Motion☆

Abstract: This present study deals with the fabrication of aluminium/boron carbide metal matrix composite and investigation on its tribological behavior. The composite incorporated with 5 wt% of boron carbide particles with an average size 33 μmwas fabricated through stir casting process. The microstructure of this composite was examined and uniform distribution of reinforced particles in the matrix was observed. Wear experiments were conducted on pin-on-disc tester based on Taguchi's L 27 orthogonal array using three process parameters such as applied load, sliding velocity and distance; each varied for three levels. Loads of 10 N, 20 N, 30 N; velocities of 1 m/s, 2 m/s, 3 m/s and distances of 1000 m, 1500 m, 2000 m were considered for analyzing the wear behavior of composite. Optimum parameters were found out using Signal-to-Noise ratio by choosing ‘Smaller-the-better’ characteristics for wear rate and coefficient of friction. Influence of individual parameter and their interactions on the responses was predicted using Analysis of Variance. Results depicted that both wear rate and coefficient of friction increases with load and decreases with velocity and distance. Worn out surfaces of the composite specimen were analyzed using Scanning Electron Microscope for predicting the wear mechanism. It was observed that, severe delamination occurred as applied load increased from 10 N to 30 N. This tribological analysis can be utilized to replace the conventional automotive materials with aluminium metal matrix composites having better wear characteristics.

Reciprocating wear behavior of 7075Al/SiC in comparison with 6061Al/Al2O3 composites

Abstract: In the present study, the reciprocating wear behavior of 7075Al/SiC composites and 6061Al/Al 2 O 3 composites that are prepared through liquid metallurgy route is analyzed to find out the effects of weight percentage of reinforcement and load at the fixed number of strokes on a reciprocating wear testing machine. The Metal Matrix Composite (MMC) pins are prepared with different weight percentages (10, 15 and 20%) of SiC and Al 2 O 3 particles with size of 36 μm. Hardness of these composites increases with increase in wt.% of reinforcement. However, the impact strength decreases with increase in reinforcement content. The experimental result shows that the volume loss of MMC specimens is less than that of the matrix alloy. However, the volume loss is greater in 6061Al/Al 2 O 3 composites when compared to 7075Al/SiC composites. The temperature rise near the contact surface of the MMC specimens increases with increase in wt.% of reinforcement and applied load. The coefficient of friction decreases with increase in load in both cases.

Process for additive manufacturing of parts by melting or sintering particles of powder(s) using a high-energy beam with powders adapted to the targeted process/material pair

Abstract: A method of fabricating parts out of metallic, intermetallic, ceramic, ceramic matrix composite, or metal matrix composite material with discontinuous reinforcement, includes melting or sintering powder particles by means of a high-energy beam. The powder used is a single powder of particles that present sphericity lying in the range 0.8 to 1.0 and of form factor lying in the range 1 to √2, each powder particle presenting substantially identical mean composition, and the grain size distribution of the particles of the powder is narrowed around the mean diameter value d50% in such a manner that: (d90%−d50%)/d50%≦0.66; and (d50%−d10%)/d50%≦0.33; with a “span”: (d90%−d10%)/d50%≦1.00.

Fabrication of Al–2 vol% Al2O3/SiC hybrid composite via accumulative roll bonding (ARB): An investigation of the microstructure and mechanical properties

Abstract: An Al/Al2O3/SiC hybrid metal matrix composite was fabricated by accumulative roll bonding (ARB). A mixture of Al2O3 and SiC (2 vol%) powders was poured between four Al layers during the first two ARB cycles. The process was continued up to eight cycles without adding the powders in subsequent cycles. For comparison, non-reinforced (monolithic) Al was also processed by ARB under the same conditions. At the initial stages, particle free zones as well as particle clusters were observed on the microstructure of the composite. After eight ARB cycles, a composite with a uniform distribution of particles was produced. At this stage, the tensile strength of the hybrid composite and the monolithic Al reaches to about 195 MPa and 150 MPa, respectively, about 5.3 and 4 times larger than that of annealed Al. The hardness of the composite and the monolithic Al was measured as 83 and 58 VHN, respectively. Fracture surface after tensile testing revealed dimples at some regions after eight ARB cycles.

Synthesis and characterization of Fe–ZrO2 metal matrix composites:

Abstract: This investigation reports the phase, microstructure and hardness of ZrO2-reinforced iron-based metal matrix composites synthesized by powder metallurgy. The process involved the preparation of hom...

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

Abstract: Magnesium AM60 based metal matrix composites (MMCs) reinforced with alumina (Al 2 O 3 ) fibre and/or particles were successfully fabricated by a perform-squeeze casting technique under an applied pressure of 90 MPa. Tensile properties of unreinforced AM60 alloy, Al 2 O 3 fibre/AM60 alloy metal matrix composite, and hybrid composite containing both Al 2 O 3 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.