Makina Mühendisliği

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Browsing Makina Mühendisliği by Subject "Aluminum alloys -- Heat treatment."

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    Hot-torsion experiments on aluminum and aluminum alloys
    (Thesis (M.S.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 1986., 1986.) Balkır, Ufuk.; Altıntaş, Sabri.
    In this study, the effects of temperature and strain rate on the deformation behaviour of aluminum 1100 and aluminum 2024 are investigated. The fundamentals of hot-torsion tests are briefly reviewed and testing methods are explained in detail. Then two important concepts used in data evaluation are introduced: critical radius and effective length. In the experimental work, specimens are tested at different temperatures and strain rates under the effect of torsional loading. For both materials, temperature and strain rate are found to be effective not only on the magnitude of the flow stress, but on the shape of the flow curve as well. The strain-rate-sensitivity of materials increased parallel to the increase in temperature.
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    Investigation of extrudability of different aluminum alloys by using the method of hot extrusion
    (Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2005., 2005.) Çıtak, Hasan Cem.; Altıntaş, Sabri.; Yılmaz, Metin.
    Aluminum extrusion is a very important forming process in metal industries. Byusing different dies and technologies, high variety of products can be produced byusing the method extrusion. Extrudability is an important parameter for extrusion processes. For evaluating extrudability of a material not only force and energyrequirements must be investigated but also surface quality and mechanical properties ofproduct must be considered properly.In this study, by using the method hot extrusion, extrudabilities of AA 6063 andAA 7075 aluminum alloys are investigated. Furthermore, by using die-bearing angled dies with relief and choke systems, effect of die-bearing angle on the extrudability ofthese alloys is tried to be evaluated. Three different choke dies with die-bearing angleof 1.5o choke , 1o choke , 0.5o angle, one type of relief die with die-bearing angle of 0.3o relief adding to all these a standard extrusion die, with no angle system is used forexperiments. During experiments, AA 6063 and AA 7075 alloys are used as billetswith 30 mm diameter and 80 mm length. A special designed hydraulic hot extrusionpress with 350 bars of maximum extrusion pressure is used for extruding the billets. Inorder to discuss results of experiments properly, SEM images of samples are obtained, for detecting surface qualities of samples roughness test is conducted and for evaluatingmechanical properties of samples, tensile test and hardness test are made. Also forinvestigating flow behaviours of samples during extrusion a special microstructuralstudy is made.