ساخت و بررسي مكانيزم تشكيل نانو كامپوزيت Fe,Cr)3Al-Al2O3) با روش آلياژسازي مكانيكي

چكيده انگليسي :

Synthesis and Formation Mechanism of Fe Cr 3Al Al2O3 Nanocomposite by Mechanical Alloying Sayyed Erfan Aghili Email address e aghili @ma iut ac ir Date of Submission Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor s Name Mohammad Hossein Enayati Associate Professor ena78@cc iut ac ir Fathallah Karimzadeh Associate Professor karimzadeh f@cc iut ac irAbstractIron aluminides have received considerable attention as a structural material because of theiradvantageous properties in particular high specific strength relatively high wear resistance andhardness high melting point high oxidation and corrosion resistance However industrial applicationof these alloys has been limited due to their brittleness at room temperature and their poor creepresistance above 600 C Several approaches were attempted to improve their major drawbacks such asreducing the grain size to nanometric range dispersion strengthening and addition of alloying elementssuch as Cr Taking all these factors into account the synthesis of particulate reinforced FeAl Cr intermetallic compound composite with nanostructured matrix can be interesting The reinforcementparticles can be either directly added to the matrix ex situ technique or formed by an in situdisplacement reaction One possible route for in situ introducing hard particles in the matrix ofcomposites is the mechanochemical processing in which high energy milling promotes thedisplacement reaction in a mixture of reactive powders In this study fabrication and formationmechanism of alumina reinforced Fe Cr 3Al matrix nanocomposite via mechanochemical processinghave been investigated In first stage formation mechanism of Fe Cr 3Al intermetallic compound byball milling of Fe Al Cr powder mixture has been studied In second stage Fe Cr 3Al Al2O3nanocomposite were fabricated using two routes ball milling of Fe Al Cr2O3 powder mixture and ballmilling of Fe2O3 Al Cr powder mixture The structural evaluation of powders was studied by X raydiffraction XRD transmission electron microscopy TEM scanning electron microscopy SEM and differential thermal analysis DTA and microhardness measurements Results showed that in earlystages of ball milling of Fe50Al25Cr25 powder mixture a composite lamellar structure of Fe Cr and Alis formed in which the dissolution of Al and Cr atoms in Fe lattice takes place The resulting solidsolution finally leads to the formation of nanocrystalline disordered Fe Cr 3Al phase It was found thatduring milling of Fe Al Cr2O3 system Al gradually reacts with Cr2O3 leading to the formation ofmetallic Cr and Al2O3 phases The reduced Cr and remaining Al concurrently diffuse into the Fe latticeand as a result a Fe Al Cr solid solution develops This structure transformed to Fe Cr 3Alintermetallic compound at longer milling times In Fe2O3 Al Cr system a combustion reactionoccurred between Al and Fe2O3 during milling and the heat released from this exothermic reaction leadto the in situ formation of Al2O3 nanoparticles in Fe Cr Al solid solution matrix which transformed to Fe Cr 3Al intermetallic compound after 10 h milling times Also mechanical alloying of Fe Al Cr Cr2O3 and Fe Al Cr Fe2O3 powder mixtures led to the formation of Fe Cr 3Al 20vol Al2O3nanocomposite by gradual reduction of Cr2O3 and Fe2O3 by Al The products of this reaction were Fe Cr 3Al intermetallic compound and amorphous Al2O3 Heat treatment of this compound at 900oCfor 1h led to the crystallization of Al2O3 Fe Cr 3Al 20vol Al2O3 nanocomposite powder fabricatedby mechanical alloying of Fe Al Cr and Fe2O3 was isoststically cold pressed and then sintered at1400 C for 1 hour The consolidated part had an ultrafine uniform structure consisting of aninterconnected network of Fe Cr 3Al and Al2O3 phases This structure had a hardness value of 626 Hvwhich is much higher than that for similar material fabricated by other methods KeywordsIron aluminides nanocomposite mecha

عقيلي، عرفان

ساخت و بررسي مكانيزم تشكيل نانو كامپوزيت Fe,Cr)3Al-Al2O3) با روش آلياژسازي مكانيكي

تركيبات بين فلزي , آلومينايدهاي آهن , فرايند مكانوشيميايي