Recep Çalın

The effect of reinforcement volume ratio on porosity and thermal conductivity in Al-Mgo composites

In this study, the effects of reinforcement volume ratios (RVR) on composite structure and thermal conductivity were examined in Al-MgO reinforced metal matrix composites (MMCs) of 5%, 10% and 15% RVR produced by melt stirring. In the production of composites, EN AW 1050A aluminum alloy was used as the matrix material and MgO powders with particle size of -105 µm were used as the reinforcement material. For every composite specimen was produced at 500 rev/min stirring speed, at 750 °C liquid matrix temperature and 4 minutes stirring time. Composite samples were cooled under normal atmosphere. Then, microstructures of the samples were determined and evaluated by using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis. In general, it was observed that the reinforcement exhibited a homogeneous distribution. Furthermore, it was determined that the increase in the RVR increased porosity. From the Scanning Electron Microscope images, a thermal Ansys model was generated to determine effective thermal conductivity. Effective thermal conductivity of Al-MgO composites increased with the decrease in reinforcement volume ratio.

Effect of T7 heat treatment on the dry sliding friction and wear properties of the SiC-reinforced AA 2014 aluminium matrix composites produced by vacuum infiltration:

Dry sliding wear properties of SiC-reinforced AA 2014 aluminium matrix composites produced by vacuum infiltration method were investigated using a pin-on-disc test machine after examining their microstructural and mechanical properties. It was observed that the porosity of the composites decreased with increasing volume ratio up to 2% SiC; above this level, porosity of the composites reached almost constant levels. The hardness of the composites increased continuously with increasing SiC content. It was observed that T7 heat treatment increased the wear resistance and removed the dendritic structure of the produced composites. The highest wear resistance was obtained from AA 2014-2%SiC composite both as-cast and heat-treated conditions. Wear resistance of the composites tested was observed to be strongly dependent on their porosity rather than their other properties.

Investigation of machinability in Al-MgO composites produced by melt-stirring

Abstract In this study, Al-MgO reinforced metal matrix composites of 5%, 10% and 15% reinforcement-volume ratios were produced by melt-stirring and subjected to machining tests by carbide and coated carbide cutting tools. Machining tests were conducted with 150, 200, 250 and 300 m/min cutting speeds, 0.075, 0.15 and 0.225 mm/rpm feed rates and 1 mm depth of cut. Piezoelectric quartz crystal type dynamometer was used to measure cutting forces. As a result of the tests, it was observed that the increase in cutting speed first led to an increase and then a decrease in main cutting force values (Fc), and the increase in feed rate was accompanied with increased main cutting forces. The most consistent results in terms of Fc values were displayed by 10% MgO reinforced composites. While no abrasion occurred on the surfaces of cutting tools, build up edge formation was observed in the machining tests.

Effect of matrix temperature and powder size on the infiltration height of SiO2-reinforced Al 7075 matrix composites produced by vacuum infiltration

Abstract In this study, the effect powder size and matrix temperature on the physical and mechanical properties of SiO2-reinforced Al 7075 matrix composites were investigated. It was observed that with increasing powder size and temperature, infiltration height was increased. Optimum parameters of full infiltration that were determined for particle size and temperature were d50=150 μm and 800°C, respectively. It was also observed that the porosity of the produced composites changed in the range of 3.2–14.6%, and the lowest porosity was obtained from the composite having 105 μm SiO2 particle size. The highest fracture strength (263 MPa) was obtained from the composite produced at a matrix temperature of 800°C and a particle size of 420 μm. It was concluded that particle size and temperature are effective parameters to reach full infiltration, and this method is more suitable for producing the composites that have high reinforcement volume fractions than conventional casting methods.

An Investigation on the Microstructure and Wear Properties of TiB2 Reinforced AA2014 Aluminium Alloy Produced by Vacuum Infiltration

Abstract In this study, microstructural, mechanical and wear properties of TiB2 reinforced Al 2014-based composites produced by vacuum infiltration were investigated under different production temperatures. It was observed that the microstructures of the composites consisted of Al matrix and TiB2 particles. TiB2 particles exhibit various shapes such as cubic, triangle and spherical. It was observed that the hardness and porosity of the composites increased with increasing TiB2 content. It was also observed that the production temperature has an important effect on the porosity and hardness of the produced composites. The highest wear resistance was obtained from Al 2014-8% TiB2 composite among the materials tested. It was observed that the production temperature and hardness are effective parameters on wear of produced composites. Evaluation of microstructural and mechanical test results suggest that it would be beneficial to keep the production temperature around 800 °C and Al 2014-8% TiB2 composite can be recommended for engineering applications where the hardness and wear resistance are considered to be significant factors.