V. Auradi

Effect of Al 2 O 3 Particles on Mechanical and Wear Properties of 6061al Alloy Metal Matrix Composites

Particulate reinforced aluminium matrix composites are being considered for their superior mechanical and tribological properties over the conventional aluminium alloys, and therefore, these composites have gained extensive applications in automotive and aerospace industries. In this investigation, the fabrication of 6061Al composites with different weight percentage of Al2O3 particles up to 0-9% was processed by liquid metallurgy route. For each composite, reinforcement particles were preheated to a temperature of 200°C and then dispersed in steps of three into the vortex of molten 6061Al alloy rather than introducing all at once, there by trying to improve wettability and distribution. Microstructural characterization was carried out for the above prepared composites by taking specimens from central portion of the casting. Microstructural characterization of the composites has revealed fairly uniform distribution of Al2O3 particulates. XRD analysis revealed the presence of Al2O3 and other phases. The tensile strength and hardness of the resultant composites were examined. It was revealed that the 6061Al- Al2O3 composites have a higher tensile strength than 6061 aluminium alloy with reduced ductility. It was found that an increase in the Al2O3 content in 6061Al alloy contributed in enhancing the hardness of the composites. The wear test was conducted using computerized pin on disc wear tester with counter surface as EN31 steel disc (HRC60) and the composite pin as specimens, demonstrated the superior wear resistance property of the composites.

Influence of particle size on Cutting Forces and Surface Roughness in Machining of B4Cp - 6061 Aluminium Matrix Composites

Amongst advanced materials, metal matrix composites (MMC) are gaining importance as materials for structural applications in particular, particulate reinforced aluminium MMCs have received considerable attention due to their superior properties such as high strength to weight ratio, excellent low-temperature performance, high wear resistance, high thermal conductivity. The present study aims at studying and comparing the machinability aspects of B4Cp reinforced 6061Al alloy metal matrix composites reinforced with 37μm and 88μm particulates produced by stir casting method. The micro structural characterization of the prepared composites is done using Scanning Electron Microscopy equipped with EDX analysis (Hitachi Su-1500 model) to identify morphology and distribution of B4C particles in the 6061Al matrix. The specimens are turned on a conventional lathe machine using a Polly crystalline Diamond (PCD) tool to study the effect of particle size on the cutting forces and the surface roughness under varying machinability parameters viz., Cutting speed (29-45 m/min.), Feed rate (0.11-0.33 mm/rev.) and depth of cut (0.5-1mm). Results of micro structural characterization revealed fairly uniform distribution of B4C particles (in both cases i.e., 37μm and 88μm) in 6061Al matrix. The surface roughness of the composite is influenced by cutting speed. The feed rate and depth of cut have a negative influence on surface roughness. The cutting forces decreased with increase in cutting speed whereas cutting forces increased with increase in feed and depth of cut. Higher cutting forces are noticed while machining Al6061 base alloy compared to reinforced composites. Surface finish is high during turning of the 6061Al base alloy and surface roughness is high with 88μm size particle reinforced composites. As the particle size increases Surface roughness also increases.

Dry Sliding Wear Behavior of Graphite Particulate Reinforced Al6061 Alloy Composite Materials

This present paper is an investigation made to study the un-lubricated sliding wear behavior of Al6061 alloy composites reinforced with graphite particulates of size 100-125 μm. The content of graphite in the alloy was varied from 6-9% in steps of 3 wt. %. The liquid metallurgy technique was used to fabricate the composites. A pin-on-disc wear testing machine was used to evaluate the volumetric wear loss, in which a hardened EN32 steel disc was used as the counter face. The results indicated that the volumetric wear loss of the composites was lesser than that of the Al6061 matrix alloy and it further decreased with the increase in graphite content up-to 6 wt.%. For composites containing 9 wt. % of graphite particulates, the volumetric wear loss was more than that of 6wt. % composites, but lesser than base matrix alloy. However, the material loss in terms of wear volume increased with the increase in load and sliding speed, both in case of composites and the alloy.

Microstructure and Mechanical Properties of Al6061-Graphite Composites Fabricated by Stir-Casting Process

In the present study, the experimental results of the mechanical properties of Al6061-Graphite composites presented. The composites containing 6 to 9 wt% of graphite in steps of 3 wt% were prepared using liquid metallurgy route in particular stir casting technique. For each composite, reinforcement particles were preheated to a temperature of 250°C and then dispersed in steps of two into the vortex of molten Al6061 alloy to improve the wettability and distribution. Microstructural characterization was investigated by optical and scanning electron microscopy. Tensile and hardness tests were carried out in order to identify mechanical properties of composites. The results of microstructural study revealed uniform distribution of graphite particles and low porosity in micro composite specimens.The results of this study revealed that as graphite percentage was increased, there was significant increase in ultimate tensile strength, yield strength and ductility, accompanied by a nominal drop in the hardness of the material

Mechanical and Tribological Behaviour of Epoxy Reinforced with Nano Al2O3 Particles

In the present work systematic study has been conducted to investigate the matrix properties by introducing nanosize Al2O3 (particle size 100 nm, 0.5–10 wt %) fillers into an epoxy resin. High shear mixing process was employed to disperse the particles into the resin. The experimental results indicated that frictional coefficient and wear rate of epoxy can be reduced at rather low concentration of nanoAl2O3. The lowest specific wear rate 0.7 x 10-4 mm3/Nm is observed for the composites with 1 wt.% which is decreased by 65% as compared to unfilled epoxy. The reinforcement of Al2O3 particles leads to improved mechanical properties of the epoxy composites. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms.

Mechanical Behaviour and Dry Sliding Wear Properties of Ceramic Boron Carbide Particulate Reinforced Al6061 Matrix Composites

ABSTRACT An attempt has been made to evaluate the mechanical behaviour and wear properties of Al6061-9 wt% B4Cp composite prepared by stir casting. During the preparation of composites, K2TiF6 salt is used as flux to increase wettability of B4Cp at low temperature and also two step introduction of the mixture containing B4Cp and K2TiF6 flux (ratio of 0.3) is adopted to achieve better dispersion. Characterization of the prepared composites is done using XRD/SEM/EDS studies. Microstructural characterization has revealed fairly uniform dispersion of B4Cp in Al6061 matrix with clustering at few places. X-ray diffraction pattern taken on the prepared composite clearly reveals the presence of α-Al, B4C, Ti compound layer (Al3Ti/TiB2), AlB2 and Al3BC. Mechanical properties of the prepared composites such as hardness, UTS and specific strength have been improved by 115.3%, 38.8% and 42.8% respectively in comparison with matrix alone. Further, fractography studies conducted on the tensile specimens revealed both ductile and brittle types of fracture in Al6061-B4Cp composites. Results of wear studies clearly suggest that addition of B4Cp into Al6061 matrix has reduced the wear rate by restricting dislocation pile up formed at the Al-B4Cp interface and also the formation of tribolayers between the contact surfaces reduces wear rate. GRAPHICAL ABSTRACT

Experimental Investigations on Effect of Ceramic B4C Particulate Addition on Cutting Forces and Surface Roughness during Turning of 6061Al Alloy

ABSTRACT Aluminium matrix composites are of great interest for researchers in recent years because of their excellent combinations of engineering properties over traditional materials. The machinability of these aluminium matrix composites has become vital for manufacturing industries. During machining of aluminium matrix composites, the cutting forces and surface roughness are dependent on machining parameters (feed rate, cutting speed and depth of cut) and manufacturing parameters (size of the particles, volume fraction, porosity, hardness). With this backdrop, the present work is aimed at investigating the effect of machining parameters, viz. cutting speed, feed rate and depth of cut on the cutting force components, namely, feed force (Ff), radial force (Fd), cutting force (Fc) and surface roughness. The experiments were performed on 0, 5, 7 and 9 wt% B4C particulate of 88 µm size reinforced composite specimens. The prepared specimens were subjected to turning operation on a conventional lathe machine using polycrystalline diamond (PCD) tool to evaluate the effect of B4C particulate addition with varying percentages on cutting forces and surface roughness. Results reveal that the cutting force components decrease with the increase in the wt% of ceramic B4C particulate reinforcement, which can be attributed mainly to increase in porosity, hardness and dislocation densities. SEM image obtained from composite having low wt% of ceramic B4C particulates (5 wt%), which is machined at higher cutting speed and higher depth of cut, has clearly shown the presence of built-up edge (BUE) at the tip of polycrystalline diamond tool. Further, cutting forces increased with increase in feed rate and depth of cut for both 6061Al matrix and 6061Al-B4C composites. It is observed that the surface quality is significantly improved when the cutting speed is increased, and depth of cut and feed rate are decreased. GRAPHICAL ABSTRACT

Effect of SiC and Graphite Particulates Addition on Wear Behaviour of Al2219 Alloy Hybrid Composites

In this investigation wear behaviour of A12219 alloy reinforced with SiC and graphite particulates were studied. The percentage of silicon carbide and graphite as reinforcements were varied from 2 wt.% to 4 wt.% in steps of 2. Energy dispersive spectroscopy and scanning electron microphotographs were used to confirm the presence of SiC and graphite particulates and its uniform distribution over the aluminum matrix. Wear behaviour of aluminum alloy Al2219 reinforced with silicon carbide and graphite fabricated by stir casting process was investigated. The wear properties of the metal matrix composites were studied by performing dry sliding wear test using a pin-on-disc wear tester. The experiments were conducted at a constant sliding velocity of 1.73m/s over a load of 2kg. The results showed that the wear resistance of Al2219-2%SiC-2% graphite and Al2219-4%SiC-4% graphite composites were better than the unreinforced alloy. The wear in terms of weight loss and wear rate was found to decrease with the increasing the weigh percentages of SiC and graphite. To study the dominant sliding wear mechanism worn surfaces were analyzed using scanning electron microscopy.

Microstructure and Mechanical Characterization of Al-Tib2 In Situ Metal Matrix Composites Produced via Master Alloy Route

In the present work, Al-TiB2 in-situ metal matrix composites were processed via master alloy route at 800°C-30 min. with 5 and 7wt% of TiB2 particles. Microstructural characterization of the prepared insitu composites were carried out using XRD, SEM/EDX studies. X ray diffraction studies have shown the presence of Al3Ti and TiB2 phases, however, the presence of AlB2 particles is also highly likely. SEM/EDX characterization revealed fairly uniformly distributed TiB2 particles having hexagonal morphology with size distribution in the ranges between 0.5-10μm. Further, presence of TiB2 particles in Al matrix have resulted in improvement in hardness and tensile properties of the Al matrix while decrease in ductility was observed.

Processing and Microstructural Characterization of Cermet-Reinforced Aluminium Matrix Composite by Solidification Process

The present work deals with the preparation of the aluminium matrix composite using a ceramic and metallic combination as reinforcements and using liquid metallurgy route of solidification process. The desired properties of composites have been influenced by the solidification behaviour of the cast metal matrix composites, which has been imposed to study the solidification behaviour of metal matrix at different weight fraction of reinforcement particulates. Al7075 was used as matrix and tungsten carbide, and cobalt particulates were used as reinforcements. During the preparation, an addition of magnesium was used to increase the wettability of the particulates during the mixing. XRD/EDX/SEM characterizations of the prepared composites were conducted, where a fairly uniform distribution of the reinforced particulates was found over the matrix.