Person: TÜNÇAY, MEHMET MASUM
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TÜNÇAY
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MEHMET MASUM
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Publication Open Access Evaluation of the Particle Bonding for Aluminum Sample Produced by Spark Plasma Sintering(SPRINGER, 2016-10) TÜNÇAY, MEHMET MASUM; Tuncay, Mehmet Masum; Nguyen, Lucie; Hendrickx, Philippe; Brochu, MathieuSpark plasma sintering (SPS) is a powder metallurgy process that sinters powder materials within a short time by simultaneous application of electrical current and pressure. SPS differs from other conventional powder metallurgy processes by its heating mechanism, which is Joule heating of the sample within a graphite die. This study investigates the consolidation of aluminum powder by SPS. Different pressures were used and particle bonding evaluated by means of fracture surface analysis. Electrical resistance, obtained from online monitoring of the variation of voltage and current during the process, showed an enhanced descent at 0.3 T (m), and the area under this drop was associated with ductility: the greater the area, the higher the ductility. This temperature corresponds to a significant increase in the hardness ratio of the oxide layer to aluminum, where breakdown of the oxide layer becomes easier, permitting enhanced metallurgical bonding between the powder particles.Publication Open Access Spark plasma sintering and spark plasma upsetting of an Al-Zn-Mg-Cu alloy(ELSEVIER SCIENCE SA, 2017-09) TÜNÇAY, MEHMET MASUM; Tuncay, Mehmet Masum; Muniz-Lerma, Jose Alberto; Bishop, Donald Paul; Brochu, MathieuAl-Zn-Mg-Cu alloy powder Alumix 431D was sintered at 400 degrees C by spark plasma sintering (SPS) and upset forging was applied to the sintered sample through SPS. Densities of 99.1 +/- 0.3% and 99.8 +/- 0.1% of theoretical were obtained for the sintered and forged samples, respectively. T6 temper was carried out on the samples and microstructure analysis and mechanical properties before and after heat treatment were evaluated. Microhardness of 173 +/- 3 and 172 +/- 3 HV were attained in the T6 temper of as-sintered and forged samples, respectively. The flexural strength and strain values were significantly improved after the forging process, which can be mainly attributed to the better particle bonding in addition to the occurrence of some recrystallization. Significant loss in the ductility was observed after the T6 temper.Publication Open Access Spark Plasma Sintering and Upsetting of a Gas-Atomized/Air-Atomized Al Alloy Powder Mixture(SPRINGER, 2017-10) TÜNÇAY, MEHMET MASUM; Tuncay, Mehmet Masum; Muniz-Lerma, Jose Alberto; Bishop, Donald Paul; Brochu, MathieuAl-Zn-Mg-Cu alloy powder, Alumix 431D, was modified by replacing the native air-atomized pure Al particles with gas-atomized pure Al. Samples were sintered using spark plasma sintering (SPS), and upset forging was applied to the sintered samples by SPS. Densities over 98 and 99% of theoretical were obtained for the sintered and forged samples, respectively. Microstructural analysis and characterization of all samples were done using energy-dispersive spectroscopy and x-ray diffraction. Mechanical properties were evaluated using microhardness and flexural strength and strain measurements. The microhardness value of the T6 tempered sample was comparable to that of its wrought counterpart AA7075. Particle bonding after sintering was incomplete and reveals that composite oxide layer of Al-Zn-Mg-Cu alloy powder is difficult to disrupt, and it is necessary to apply a secondary process like forging to improve particle bonding. The loss in ductility following T6 tempering is ascribed to void formation due to the dissolution of the secondary phases, remaining undissolved precipitates, and a localized lack of cohesion between particles.