ساخت و بررسي خواص قطعات نانو كامپوزيت Al/Al3Zr با روش آلياژ سازي مكانيكي و اكستروژن گرم

چكيده انگليسي :

Fabrication and characterization of Al Al3Zr nanocomposite by mechanical alloying and hot extrusion Esmaeil Pourkhorshid Email e pourkhorshid@ma iut ac ir Date of Submission January 21 2014 Degree M Sc Language Farsi Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranSupervisors Mohammad Hossein Enayati ena78@cc iut ac irFathallah Karimzadeh karimzadeh f@cc iut ac irAdvisor Mohammad Hossein PaydarAbstractNumerous investigations have been performed to develop alloys suitable for aerospace industry For someaerospace and automotive applications lightweight alloys which can operate at high temperatures for longperiods are required Aluminium composite reinforced with the intermetallic particles are the most importantmaterials in this field Addition of zirconium to aluminium can produce zirconium trialuminide Al3Zr intermetallic compound which can improve the strength of Al at elevated temperature due to the very slowcoarsening rate The aim of this work was to produce bulk nanostructured Al Al3Zr by mechanical alloying MA and subsequent hot extrusion and to investigate the properties of bulk samples For this purpose theAl3Zr powders were produced by mechanical alloying MA of elemental Al and Zr powders with ball mill Al3Zr powder was then mixed with pure aluminium to prepare Al Al3Zr composite with different weightpercent of reinforcement Al3Zr This powder was consolidated by hot extrusion method at 550 C and thenthe properties of samples were evaluated The microstructural changes were studied using X ray diffraction XRD scanning electron microscopy SEM and transition electron microscopy TEM The mechanicalproperties of consolidated samples were evaluated by hardness and tension tests at room temperature andhigh temperatures In order to study the wear behavior of material pin on disk wear test was performed onconsolidated samples under loads of 27 and 40N at room temperature The results showed that after 50 hr ofMA no new phase was observed in powder mixtures After heat treatment of mechanically alloyed powder at600 C for 1 hr Al3Zr was formed The differential scanning calorimetry results showed that production ofAl3Zr began with nucleation of a metastable phase which then transforms to the stable tetragonal Al3Zr Thegrain size of Al3Zr was meatured to be 32 nm By hot extrusion of MA powders it was possible to producebulk samples with a relative density of about 99 and uniform distribution of reinforcement in the matrix The tension yield strength of Al 10 wt Al3Zr was determined to be 105 MPa which are much higher thanthat for pure Aluminium 60 MPa The tension test behavior of samples in 300 C showed that the presenceof reinforcement in structure prevented the recrystallization At temperature of 300 C the yield stress ofAl 10 wt Al3Zr was about 95 MPa The room temperature hardness of Al Al3Zr composite remainedunchanged after annealing at 300 C for 36 hr confirming high thermal stability of the material Wear testresults showed that the wear rate decreases by increasing the volume fraction of reinforcement in thecomposites The predominant mechanisms of wear depends on applied force and change from the formationof mechanical mixed layer to abrasive and then delamination with increasing force Keywords Aluminium matrix composite Al3Zr Nanostructure material Mechanical alloying Hotextrution

پورخورشيد، اسماعيل

ساخت و بررسي خواص قطعات نانو كامپوزيت Al/Al3Zr با روش آلياژ سازي مكانيكي و اكستروژن گرم

كامپوزيت زمينه آلومينيوم , مواد نانو ساختار