Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...

Laser additive manufacturing of metallic components: materials, processes and mechanisms

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.

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

Composites by rapid prototyping technology

This paper reviews the research and development works conducted over the past few decades on carbon fiber reinforced metal matrix composites (CFR-MMC). The structure and composition of carbon fiber and its bonding to metal matrix have an impact on the properties of the resulting CFR-MMC remarkably. The research efforts on process optimization and utilizing of carbon fibers are discussed in this review. The effect of carbon fiber on structural, physical and mechanical properties of metal matrix composite are studied as well. This review also provide an overview of the research to date on various fabrication methods that is used for production of CFR-MMC.

Carbon fiber reinforced metal matrix composites: Fabrication processes and properties

Tribocorrosion is an irreversible transformation of a material resulting from simultaneous physico-chemical and mechanical surface interactions in a tribological contact. Electrochemical methods are well suited for the study of tribocorrosion phenomena because they allow one to simulate the corrosive effect of the environment by imposing a fixed potential. Furthermore, the measurement of the anodic current permits one to determine the amount of material removed by oxidation as opposed to mechanical wear. In the present paper, experimental and theoretical aspects of applying electrochemical methods in tribology are discussed and recent results obtained with passivating metals in the authors' laboratory are presented. The importance of controlling the mechanical parameters and the contact geometry is stressed, and it is shown that these parameters can significantly affect the electrochemical response of a tribocorrosion system.

Electrochemical methods in tribocorrosion: a critical appraisal

Silicon nitride is currently a popular choice as reinforcement to develop light alloy composites owing to its high hot hardness and excellent wear and corrosion resistance. However, meager information is available as regards the development of aluminum alloy–silicon nitride composites by stir cast technique. This route of processing metal matrix composites (MMCs) poses challenges in particular, poor wettability of the ceramic reinforcement in the matrix alloy. To overcome this problem, researchers are currently focusing on use of metallic coated ceramic reinforcement. In the light of the above, this paper discusses the development of Ni–P coated silicon nitride reinforced Al6061 composites by stir cast method. XRD, metallographic, EDAX studies, microhardness, and tensile strength tests of the developed composites have been carried out. A maximum of 10 wt% of Ni–P coated silicon nitride has been dispersed uniformly in the matrix alloy. A drastic improvement in both microhardness and tensile strength is observed.

Microstructure and mechanical properties of Ni–P coated Si3N4 reinforced Al6061 composites

Development and performance analysis of novel cast copper–SiC–Gr hybrid composites

Prediction of wear coefficient of Al6061–TiO2 composites

In situ reinforced aluminium based metal matrix composites (AMMCs) are emerging as one of the most promising alternatives for eliminating the inherent defects associated with ex situ reinforced AMMCs. Researchers in recent past have attempted various processing techniques for the development of in-situ composites, of which liquid metallurgy is the most widely adopted technique. Development of in-situ composites via liquid metallurgy route using master alloys is a relatively new processing technique. Very little information is available providing the usage value of these reinforcing materials.

The present study is an attempt to explore the processing and characterization of in situ AMMCs using master alloys as reinforcement materials. Al 6061–TiB2 in-situ composites were fabricated by liquid metallurgy route using Al 6061 as the matrix material and Al–10%Ti and Al–3%B as reactive reinforcements. Tests carried out on the fabricated composites include XRD, metallographic studies, EDAX analysis, microhardness, grain size analysis and tensile strength tests. The developed composites exhibited superior structural properties when compared with base alloy.

C.S. Ramesh

Papers

Microstructure and mechanical properties of Ni–P coated Si3N4 reinforced Al6061 composites

Development and performance analysis of novel cast copper–SiC–Gr hybrid composites

Prediction of wear coefficient of Al6061–TiO2 composites

A study on microstructure and mechanical properties of Al 6061–TiB2 in-situ composites

Friction and wear behavior of Ni–P coated Si3N4 reinforced Al6061 composites