Y. Sahin

Preparation and some properties of SiC particle reinforced aluminium alloy composites

Aluminium alloy composites containing various particle sizes of 10 and 20 wt.% SiC particles were prepared by molten metal mixing and squeeze casting method under argon gas. The stirring was carried out with graphite impeller during addition of particle. The molten mixture was poured into a die when the stirring was completed and metal matrix composites were produced by applying the pressure. Optical microscopic examination, hardness, density and porosity measurement were carried out. Moreover, metal matrix composites were machined at various cutting speeds under a fixed depth of cut and feed rate using different cutting tools. It is observed that there was a reasonably uniform dispersion of particles in the matrix alloy. The density decreased with decreasing particle sizes, but porosity decreased considerably with increasing particle size. In addition, the tool life decreased considerably with increasing cutting speeds for all tests. Among cutting tools, the wear resistance of Al2O3 coated tools showed better performance than those of the other tools without chip breaker geometries in the machining of SiCp-reinforced composites.

Wear behaviour of aluminium alloy and its composites reinforced by SiC particles using statistical analysis

Abstract The wear behaviour of SiCp-reinforced aluminium composite produced by the molten metal mixing method was investigated by means of a pin-on-disc type wear rig. Abrasive wear tests were carried out on 5 vol.% SiCp and its matrix alloy against SiC and Al2O3 emery papers on a steel counterface at a fixed speed. The wear rate of the composite and the matrix alloy has been expressed in terms of the applied load, sliding distance and particle size using a linear factorial design approach. The parameters x1, x2 and x3 are the code values of sliding distance, applied load and abrasive size, respectively. It has been demonstrated through established equations that the composite exhibited a low wear rate compared to the unreinforced matrix material for both cases. Moreover, the wear rate increased with increasing applied load, abrasive size and sliding distance for SiC paper, whereas the wear rate increased with applied load and abrasive particle, and it decreased with sliding distance for Al2O3 paper. The interaction effect of the variables exhibited a mixed behaviour towards the wear of the materials.

Production and properties of SiCp-reinforced aluminium alloy composites

A vacuum infiltration process was developed to produce aluminium alloy composites containing various volume fractions of ceramic particles. The matrix composites of aluminium with 9.42 wt%Si and 0.36 wt%Mg containing up to 55 vol% SiCp were successfully infiltrated and the effect of infiltration temperature and volume fraction of particle on infiltration behaviour was investigated. In addition to aluminium powder, magnesium was used to improve the wetting of SiC particles by the molten aluminium alloy. The infiltration rate increased with increasing infiltration time, temperature and volume fraction of particle, but full infiltration appeared at the optimum process parameters for the various volumes of fraction composite compacts. In addition, the microstructure, hardness, density, porosity and wear resistance of the composites were also examined. It is observed that the distribution of SiC particles was uniform. The hardness and density of the composite increased with increasing reinforcement volume fraction and porosity decreased with increasing particle content. Moreover, the wear rate of the composite increased with increasing load and decreased with increasing particle content.

The effect of Al2O3, TiN and Ti (C,N) based CVD coatings on tool wear in machining metal matrix composites

Abstract The effect of Al 2 O 3 , TiN and Ti (C,N) based CVD coatings on tool wear in machining metal matrix composites containing 10 wt.% SiC particles produced by liquid metallurgy was investigated at different cutting conditions. In turning tests, various cutting speeds and two cutting tools having different chip breaker geometry were used at a constant feed rate and depth of cut. The results showed that the tool life decreased considerably with increasing particle size and cutting speed in machining the particle-reinforced composite. The wear performance of TiN-coated tool was considerably lower than that of Al 2 O 3 -coated tool in machining the composites with various particle sizes. Cutting speed was also found to be more effective in machining the composite. Moreover, it was observed that mild abrasive was the main responsible mechanism for wear of the tool.

The effect of sliding speed and microstructure on the dry wear properties of metal-matrix composites

Abstract The effects of sliding speed and microstructure on the dry wear and friction properties of unreinforced 2014 aluminium alloy matrix and its unidirectional boron fibre-reinforced composites were investigated. Tests were conducted on the composites with fibres oriented normal and parallel to the sliding direction, rubbing against a rotating steel disc at speeds of 0.6, 1.0 and 1.6 m s −1 under different loads. Wear surfaces and subsurface sections of the wear samples of the matrix and composites were examined by scanning electron microscopy after wear testing. The metal-matrix composites showed excellent wear resistance compared with the unreinforced matrix, but the orientation of the fibres with respect to the sliding direction was found to affect the wear rates. The normal orientation (N) displayed a better wear resistance than the parallel orientation (P) when the tests were conducted at speeds of 0.6 and 1.0 m s −1 , but there was little difference at the highest speed of 1.6 m s −1 . The presence of fibres reduced the amount of surface damage and subsurface plastic deformation for both sliding directions. The fibres in the surfaces of the N-oriented samples were chipped at the ends during wear tests, and the detached fragments of fibre became embedded into the soft aluminium alloy matrix, giving a low wear rate, especially at low sliding speed. At higher speeds more rapid wear occurred, but the onset of oxidative wear at the highest speed of 1.6 m s −1 gave a very low wear rate. In the P-oriented samples, at low speed, many segments of fibres were pulled out from the wear surfaces owing to friction against the disc, and surface ploughing occurred, giving a high wear rate which mostly peaked at 1.0 m s −1 . At the highest speed fibre fragmentation replaced pull-out and the small fibre fragments remained embedded in the surface, which with the development of surface oxides, reduced the wear rate to its minimum value. In general the friction coefficient of the matrix and composites decreased with increased sliding speed, but many tests showed a peak at a speed of 1.0 m s 1 . The matrix had a lower friction coefficient than the composites, and at the lower load the friction coefficient increased with fibre content for both fibre orientations, but at the higher load behaviour was erratic owing to the opposing effects of fibre fracture and matrix oxidation. For the P-orientation the friction coefficients of the composites were lower than those of the N-orientation, and most peaked at the intermediate speed.

Wear behaviour of planar-random fibre-reinforced metal matrix composites

Abstract The wear behaviour of δ-alumina fibre-reinforced aluminium–zinc–copper alloy composites produced by squeeze casting was investigated using a pin-on-disc wear machine. Samples of metal matrix composites were tested in the normal and planar-random orientations sliding against a smooth steel counter-surface disc at a fixed speed under different loads without lubrication. Wear surfaces of the MMCs and of their matrix alloy were also examined in a scanning electron microscope. The experimental results showed that the composite exhibited a low wear rate compared to the unreinforced matrix material. The wear rate decreased with an increase in volume fraction of fibre, and increased with increasing load. The optimum wear resistance occurred when most of the fibres were oriented normal to the sliding surface. Scanning electron microscopy of the worn surfaces showed that microfracture of the fibre, and reattachment of a fragmented surface layer in the normal orientation, and large scale microfracture of the fibre, and subsurface delamination were the principal mechanisms of wear in the planar-random orientation composites. Oxidation and partial delamination were predominant in the unreinforced matrix alloy.

Wear performance of aluminium alloy composites containing unidirectionally-oriented silicon carbide coated boron fibres

The friction and wear behaviour of continuous, silicon carbide coated, unidirectional boron fibre reinforced aluminium alloy composites produced by a metal infiltration technique was investigated. A pin-on-disc type apparatus was employed for determining the sliding wear rate and the coefficient of friction in a direction normal to the fibre axis. The effects of applied load and volume fraction of fibre on the dry sliding behaviour were evaluated. The wear rates of the composites were considerably less than that of the aluminium matrix alloy at all applied loads. However the friction coefficients of the composites were found to be higher than that of the matrix alloy. Scanning electron microscopy of the worn surfaces revealed that fibre microfracture was the predominant mechanism of wear of the composites, while ploughing and delamination were the operative wear mechanisms of the aluminium alloy matrix.

The Development of Surface Roughness Model When Turning Hardened Steel with Ceramic Cutting Tool Using Response Methodology

This paper presents a study of the development of surface roughness model when turning the mild steel hardened up to 484 HV with mixed alumina ceramic (KY1615) and coated alumina ceramic cutting tools (KY4400). The model was developed in terms of main cutting parameters such as cutting speed, feed rate and depth of cut, using response surface methodology. The established equation indicated that the feed rate affected the surface roughness the most, but other parametres remined stable for arithmetic average height parametre (Ra). However, it decreased with increasing the cutting speed, and with the starting and finishing point of cut for ten point height parametre (Rz). The cutting speed and the depth of cut had a slight effect on surface roughness values of Ra, Rz when using KY4400 cutting tools. Furthermore, the average surface roughness value of Ra was about 0.926 um, 1.089 um for KY1615, KY4400 cutting tools, respectively. The predicted surface roughness was found to be very close to experimentally observed ones at 95% confidence level. Moreover, analysis of variance indicated that squares terms were significant but interaction terms were insignificant for both cutting tools.

Prediction of Surface Roughness in the Machining of Carbon Steels by Cutting Tools

The surface roughness model in the turning of AISI 1040 carbon steel was developed in terms of cutting speed, feed rate and depth of cut, using response surface methodology and design of experiment. The surface roughness equations of cutting tools when machining the carbon steels were achieved by using the experimental data. The established equations show that the feed rate was the main influencing factor on the surface roughness and it increased with increasing the feed rate for both tools. For TiN‐coated tools, the feed rate is followed by depth of cut. For cermet tools, however, the feed rate is followed by cutting speed. In addition, the cermet tools showed the better surface roughness than those of the coated cutting tools. The second order model shows that the square terms are statistically insignificant for both tools. For the cermet tools, however, the interaction terms are found to be statistically significant. The predicted wear behavior of the samples has been found to lie close to that of the ...