ساخت آلياژهاي نانو ساختار Al-Fe-V-Si با روش آلياژ سازي مكانيكي و پرس داغ و بررسي خواص آن ها

چكيده انگليسي :

Fabrication of Nanostructured Al Fe V Si Alloys by Mechanical Alloying and Hot Pessing and Study of Their Properties H Ashrafi Email address h ashrafi@ma iut ac ir Date of Submission 4 17 2012 Department of Materials Engineering IsfahanUniversity of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisors Mohammad Hossein Enayati Associate Professor ena78@cc iut ac ir Rahmatollah Emadi Associate Professor remadi@cc iut ac ir AbstractAmong the high temperature aluminum alloys Al Fe V Si system has received great attention because of itsgood properties at ambient and elevated temperatures The aim of this work was to produce bulknanostructured Al 8 5Fe 1 3V 1 7Si and Al 11 7Fe 1 3V 2 3Si alloys by mechanical alloying MA andsubsequent hot pressing and to investigate the properties of bulk samples For this purpose the Al Fe V Sialloy powders were produced by mechanical alloying MA of elemental powders and the effect of annealingon microstructure was investigated Then the as milled powders were consolidated by hot pressing method at550 C under 300 MPa for 30 minutes The microstructural changes were studied using X ray diffraction XRD scanning electron microscopy SEM and tunneling electron microscopy TEM The mechanicalproperties of consolidated samples were evaluated by hardness and compression tests Thermal stability ofalloys was studied by measuring their hardness changes after high temperature exposure In order to study thewear behavior of material pin on disk wear test was performed on consolidated samples under loads of 2 5and 10N at room temperature The results showed that after 60 h of MA no new phase was observed in Al 8 5Fe 1 3V 1 7Si and Al 11 7Fe 1 3V 2 3Si powder mixtures and the microstructure consisted ofnanostructured Al solid solution with a grain size of 19 and 21 nm respectively Isothermal annealing of asmilled powders for 1 h at temperatures between 300 and 550 C showed that at 400 C Al12 Fe V 3Si phasebegin to precipitate and at 550 C the precipitation became complete by Hot pressing of 60 h MA powders itwas possible to produce bulk samples with a relative density of about 97 The microstructure ofconsolidated samples included Al12 Fe V 3Si intermetallic phase in nanocrystalline Al matrix The hardnessvalue of bulk Al 8 5Fe 1 3V 1 7Si and Al 11 7Fe 1 3V 2 3Si nanocrystalline alloys were measured to be 205and 254 HV respectively which are 65 and 55 higher than those reported for similar alloys produced byrapid solidification The compressive yield strength of these alloys were determined to be 679 and 758 MParespectively which are about 58 and 41 higher than those of commercial alloys with same composition The results of high temperature compression test showed that the trend of strength decrease with increasingtemperature is similar to other high temperature Al alloys The room temperature hardness of Al 11 7Fe 1 3V 2 3Si nanocrystalline alloy remained unchanged after 36 h exposure to 400 C Wear test results showedthat in all applied loads the wear rate decreases by increasing the volume fraction of Al12 Fe V 3Siprecipitates The predominant mechanism of wear in Al 8 5Fe 1 3V 1 7Si and Al 11 7Fe 1 3V 2 3Sinanocrystalline alloys were determined to be formation of mechanical mixed layer on the surface of samples Keywords high temperature Al alloy Al12 Fe V 3Si compound nanostructures mechanical alloying hotpressing mechanical properties

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ساخت آلياژهاي نانو ساختار Al-Fe-V-Si با روش آلياژ سازي مكانيكي و پرس داغ و بررسي خواص آن ها

آلياژ آلومينيوم دما بالا , پرس گرم , خواص مكانيكي