6721

6272

كارشناسي ارشد

مهندسي مواد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1390

سيزده، 92ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

مسعود پنجه پور، غلامرضا آريانپور

1/3/1

جواد هاشمي فر، مهدي احمديان

1396/10/06

كتابنامه

مواد

مهندسي مواد

ID6272

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

93 Study of the Effect of Grain Boundry Structures in the Allotropic Transformation of Nanocrystalline Iron by Equation of State and Molecular Dynamics Simulation javad alizadeh j alizadehnoory@ma iut ac ir April 2 2012 Department of Mateials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiMasoud Panjepour panjepour@cc iut ac ir and Gholamreza Aryanpour arayanmat@cc iut ac irAbstract In nanocrystalline NC materials when grain size is decreased the atomic fraction of grainboundary in comparison with conventional polycrystalline materials is increased Therefore thismatter could be change the properties of this materials especially thermodynamics properties Thereupon study of thermodynamic properties of these materials with classic equations could notanswer the anomaly behavior of NC materials e g severe decrease in allotropic transformationtemperatures has been observed in NC Fe Co Al2O3 Zr and Ti For this purpose differenttheories were studied in this field and complex relations such as equation of stat EOS methodwere presented In these equations precision of calculation is strongly on accurate excess volumeand the atomic fraction values of grain boundary regions For this reason triple junction TJ andquad nodes QN that are existed in grain boundary structure must be considered in calculation ofthese values Hence to survey the precise thermodynamic properties of NC materials the maingoal of this research is calculation of values of atomic fraction of grain boundary regions andexcess volume in NC allotropic metals On the other side with not having the advancedlaboratory facilities acquisition of these values were difficult and may be impossible Somolecular dynamics simulation were used to calculate the necessary values Finally by the resultsof this simulation method the precise computation of these values were obtained Then theseresults were used for EOS entry value in study of allotropic transformation and the critical grainsize critical grain size is the grain size in which the allotropic transformation is occurred werecomputed at various temperatures The calculated critical grain size at 500K 700K and 900K are6 1nm 11nm and 15 5nm respectively These results showed that with accurate calculation ofatomic fraction and excess volume of grain boundary regions the values of critical grain sizevalues were decreased Furthermore during the computation due to the existence of someambiguity validation of equations of state is survived Thereupon these equations are evaluatedand confirmed that some errors were existed For instance could be mentioned that the equationsrelated with pressure free energy bulk modulus and enthalpy in grain boundary region is incorrect Therefore according to the equations of EOS method when the errors is eliminated the correctedprediction of thermodynamic properties were obtained Keywords Nanocrystalline Grain boundry Triple junction Quad node Grain boundaryregions Equation of state Allotropic transformation

مسعود پنجه پور، غلامرضا آريانپور

جواد هاشمي فر، مهدي احمديان