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    Effect of Alloying Time and Heat Treatment on Microstructure and Tribological Properties of Mechanical Alloyed Cu-Al-Ni Shape Memory Alloy
    (Springer, 2023) Yavuzer, Bekir; Bicakci, Unal; Simsek, Dogan; Ozyurek, Dursun
    In this study, the effects of milling time and heat treatment on microstructure and wear behavior of Cu-Al-Ni shape memory alloys produced by the mechanical alloying method were investigated. Cu-Al-Ni shape memory alloys were produced by mechanical alloying in four different durations (2.5, 5, 7.5 and 10 h) in a planetary-type mill. The produced Cu-Al-Ni shape memory alloys were characterized by microstructure (SEM + EDS), x-ray diffraction, thermal analysis (TG/DTA-DSC), and hardness, density, and dust size measurements. In the wear tests, three different loads (10, 20, and 30 N), five different sliding distances (400, 800, 1200, 1600, and 2000 m) and a sliding speed of 1 ms-1 were used. As a result of the studies, it was observed that the powder size decreased with the increase in MA time. It was observed that the density of heat-treated shape memory alloys decreased compared only to sintered alloys. According to the wear test, the lowest wear rate was obtained in Cu-Al-Ni shape memory alloys exposed to mechanical alloying for 7.5 h, with the highest hardness value. In addition, it was observed that the wear rates decreased in heat-treated Cu-Al-Ni shape memory alloys as the sliding distance increased.
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    The Effects of Small Amounts of Niobium Addition to Mechanical Alloyed AISI 304 Stainless Steel on the Microstructural and Tribological Properties
    (Springer India, 2023) Yavuzer, Bekir; Ozyurek, Dursun
    In this study, the effects of different amounts (max 1%) of niobium added to mechanical alloyed AISI 304 austenitic stainless steel on the hardness, density, microstructure, and wear behavior were investigated. After the AISI 304/Nb alloy powders were cold pressed, they were sintered in vacuum environment (10(-6) mbar) at 1300 degrees C. The produced AISI 304/Nb samples were characterized by scanning electron microscopy, X-ray diffraction, and hardness and density measurements. Wear tests were performed under dry friction at room temperature using a pin-on-disk wear device. Result of the study showed that the addition of niobium up to 0.4% increased the hardness of the alloy and improved wear behavior while greater ratios reduced the hardness of the alloy and negatively affected wear behavior. Oxidation occurred on the worn surface and lines were formed in the sliding direction. In addition, as the hardness values of the alloy increased, weight loss decreased.