P R Prabhu

Metallography & Bulk Hardness of Artificially Aged Al6061-B4C-SiC Stir Cast Hybrid Composites

Present investigation focusses on combined effect of B4C and SiC on the improvement in hardness with an average size of 35-40μm on Al6061 hybrid composite. Composites are produced by stir casting process. The effect of artificial aging treatment with different aging temperatures of 100, 150 and 200OC on the improvement in hardness is also investigated. Optical micrographs and Brinell hardness number have been discussed. An attempt is made to find out the intermetallic phase responsible for strengthening by Transmission Electron Microscopy. Due to positive response to age hardening treatment there is an improvement in the mechanical properties of Al6061 alloy & its hybrid composite. The aging kinetics is more accelerated in case of hybrid composites as compared to unreinforced Al6061 alloy because of presence of reinforcement particulate, which act as nucleation site for precipitation. Artificially aged at 100OC shows improvement in hardness by 120-220% due to the precipitation of secondary solute rich phase of alloying elements as compared Al6061 alloy.

Effect of Artificial Aging on Fracture Behavior of Al6061-Silica (SiO2) Composites

In the present work improvement in mechanical properties due to the presence of silicon oxide (SiO2) reinforced particles with an average size of 50μm and various weight percentage of (3, 6 and 9) on the hardness and fracture behaviour of Al6061-SiO2 composite is investigated. The influence of artificial aging with different aging temperatures on the mechanical properties was also assessed. Macro hardness and mechanism of fracture behaviour during tensile test have been discussed. Failure mode of fracture surface is studied to determine the parameters which influence the crack growth characteristics. Addition of SiO2 particles and artificially aging at 100°C for Al6061-SiO2 composite shows improvement in hardness by 140% and tensile strength by 60% due to the precipitation of finer secondary intermetallic phases of alloying elements. Fracture surface analysis for composite shows particle interface fracture and void nucleation growth failure.

Characteristic study for low melting point MMC using stir casting technique

This paper presents manufacturing of metallic composites using stir-casting method. The setup details and manufacturing methodology are explained. Microstructure and characterization of graphite-tin composite is also included. The tensile strength and hardness improvement is observed in tin-graphite MMC with increase in weight percentage of graphite. Metal-matrix composites (MMCs) are now attracting enormous interest. One of the prime reasons for this is that significant advances have been made in recent years on the development of fabrication routes, which are economically attractive and generate material of high micro structural quality. In particular, it is possible to produce composites, which are relatively free from gross defects (Clyne and Mason, 1987; Smith and Froes, 1984; Rodes and Spuurling, 1985; Hunt, 1989; Ted Guo and Tsao, 2000). However, it depends on the ability of synthesizing them with a consistent reproducibility in microstructure and properties. With continual development in fabricat...