Manufacturing of metal matrix composites (MMCs) through powder metallurgy route and their characterisation are the objects of the present work. Thus a light alloy reinforced with 5% of ceramics is obtained after attrition milling of mixed powders, die pressing, lubrication of compacts and hot extrusion into 10 mm diameter bars. Since 7xxx series of aluminium alloys show high mechanical properties, AA7015 alloy was chosen as metallic matrix and B4C, TiB2 and Si3N4 ceramics were added. After process optimisation, the microstructure of these materials shows a uniform distribution of ceramics in the aluminium alloy matrix. Physical properties like density, conductivity and coefficient of linear dilatation were determined on extruded MMCs samples. Hardness and tensile strength properties on machined samples according to ISO 2740 standard were evaluated. Also wear behaviour using a pin-on disk test was studied, within a microstructure study, which was carried out using optical and scanning electron microscopy.
"B 4 C have lower density than other common commercial reinforcements, such as SiC and Al 2 O 3 , resulting in a better reinforcement type for high performance MMCs . Shorowordia et al. reported that B 4 C-reinforced Al composite produced with P/M had better interfacial bonding as compared to the composites reinforced with SiC, Al 2 O 3   . However, it is difficult to obtain a uniform distribution of the reinforcing phase, which resulted in poor mechanical properties . "
[Show abstract][Hide abstract] ABSTRACT: Compression tests of 6061/B4CP composite have been performed in the compression temperature range from 300 °C to 500 °C and the strain rate range from 0.001 s−1 to 1 s−1. The flow behavior and processing map have been investigated using the corrected data to elimination of effect of friction. The processing maps exhibited two deterministic domains, one was situated at the temperature between 300 °C and 400 °C with strain rate between 0.003 s−1 and 0.18 s−1 and the other was situated at the temperature between 425 °C and 500 °C with strain rate between 0.003 s−1 and 0.18 s−1.The estimated apparent activation energies of these two domains, were 129 kJ/mol and 149 kJ/mol, which suggested that the deformation mechanisms were controlled by cross-slip and lattice self-diffusion respectively. The optimum parameters of hot working for the experimental composite were 350 °C – 0.01 s−1 and 500 °C – 0.01 s−1. In order to exactly predict dangerous damaging mechanism under different deformation conditions exactly, Gegel’s criterion was applied to obtain processing map in the paper. The result showed that the processing map used Gegel’s criterion can be effectively to predict the material behavior of the experimental composite.Highlights► The flow behavior and processing map have been investigated using the data corrected. ► Gegel’s instability criterion has been applied to establish the processing map. ► Deformation mechanisms in some deterministic deformation conditions can be predicted. ► Optimum parameters have been gained according to the processing map. ► Combining to processing map, the microstructure evolution has been researched.
"It has been reported that the interfacial bonding between the aluminum matrix and the B 4 C reinforcement seems to be better than that between aluminum and SiC (or Al 2 O 3 ) . Studies on the wear behavior of the B 4 C particulate-reinforced MMCs with Al matrices are, however , limited . In the present paper, the dry sliding friction and wear properties of MMCs with an Al-5083 matrix reinforced with B 4 C particles, which were fabricated with a powder cryomilling and consolidating process, are reported. "
[Show abstract][Hide abstract] ABSTRACT: Pin-on-disk dry sliding wear tests at sliding speeds ranging from 0.6 to 1.25 m/s and under loads ranging from 3.98 to 6.37 MPa (50–80 N) were conducted for pin specimens of composites with Al-5083 matrices reinforced with 5 and 10 wt.% B4C particles. The wear rate of the composite with 10 wt.% B4C was approximately 40% lower than that of the composite with 5 wt.% B4C under the same test condition. Two stages were observed in the reduction of pin length/sliding distance curves in several specimens, with the length reduction rate in the first stage being one to two orders of magnitude lower than that in the second stage. The low length reduction rate in the first stage corresponded with a flat stage with a low coefficient of friction (COF) in the COF/sliding distance curve.
[Show abstract][Hide abstract] ABSTRACT: Powders mixturing effects the mechanical and microstructure properties of composite materials. Mixing type of the powders; affects powder size and the distribution of the reinforcement material in matrix material. There are different types of mixing to get a homogeneous distribution of reinforcement material in matrix material. In this study, I, V and horizontal type of mixers were designed and produced. Particle reinforced Al composites materials were produced by using the powders mixed in these mixer types. B4C was used as the reinforcement materials. The reinforcement ratios of B4C in the composite material were 5%, 10% and 20% in weight. Than the powders compression in a single axis pres in 500 MPa load. These compacts were sintered in a tube furnace under argon gas controlled atmosphere for 1 hour. To characterize the composite materials; light and scanning electron microscopy examinations were done. According to the result of the experimental study, it was shown that B4C particles were fractured to smaller particles and dispersed in the composite structure which was prepared by V type mixer. The maximum hardness value was obtained with 20 % B4C particle addition in V type mixer.
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