Halil Arik

Production and characterization of in situ Al4C3 reinforced aluminum-based composite produced by mechanical alloying technique

Abstract In this study, aluminum powders were mixed with carbon black and mechanically alloyed in a high-energy ball mill for up to 30 h under argon atmosphere. XRD results showed that no Al4C3 formed during the mechanical alloying (MA) process. Mechanically alloyed powders were then compacted at 650 MPa pressure to produce transverse rupture blanks. These blanks were then sintered at 600 and 650 °C for 5, 10 and 20 h under argon atmosphere. X-Ray diffraction analysis of the sintered blocks showed the presence of Al4C3 phase. Increasing MA processing time, sintering temperature and duration, resulted in an increase in the amount of Al4C3 phase. XRD and SEM analysis showed that the most Al4C3 transformation occurred in the blank, which was mechanically alloyed for 30 h and sintered for 20 h at 650 °C. The highest hardness value (347 Hv) was obtained in this blank. Transverse rupture strengths of the sintered blanks were between 6.32 and 234.16 MPa. The highest value was obtained for the blank, which was mechanically alloyed for 15 h and sintered for 20 h at 650 °C.

Production of Si3N4 by carbothermal reduction and nitridation of sepiolite

A study was undertaken to determine the optimum parameters for production of Si3N4 powders by carbothermal reduction and nitridation (CTRN) of Turkish sepiolite. Test samples were prepared by mixing 99% purity −325 mesh carbon black and −100 mesh leached brown sepiolite with C/SiO2 molar ratios of 1.5; 3; 4; 5, and 7.5. Prepared samples were subjected to the CTRN process at temperatures of 1200, 1300, 1400 and 1450 °C for 2, 4, 8, and 16 h. The CTRN process was conducted in an atmosphere controlled tube furnace in a nitrogen flow of 4.5 cm3/min. All products were examined by XRD and SEM-EDX to determine the transformation, morphology and chemical composition. The results showed that the best Si3N4 transformation occurred at 1400 °C for 16 h with C/SiO2 molar ratio of 4.

Abrasive Wear, Structure, and Mechanical Aspects of Al–Al2O3 Composites Fabricated Using Various Mixing Media During P/M Routes

The effects of mixing method during powder metallurgy (PM) routes on the abrasive wear behavior of Al–Al2O3p composite materials is investigated. For this purpose, starting Al powders with a constant volume fraction of 10% Al2O3p are mixed in a ball-mill, Turbula, and high-energy attritor. Block samples for wear tests are prepared by using the PM process. A pin-on-disc apparatus is used for determining the wear rate. Comparative analyses are based mainly on the wear results, hardness, microstructural evaluation of the samples, and sintering densities. It is established that the samples mixed in the Turbula attritor exhibite the highest density and the lowest hardness. It is revealed that the samples mixed with Turbula have the lowest wear rate, whereas those mixed in the high-energy attritor have the highest wear rate. It is established that the composites demonstrate their optimal characteristics in the samples mixed in the ball-mill attritor.