توسعه تركيبات بين فلزي و كامپوزيت هاي نانو ساختار در سيستم سه تايي Ni-Ti-Nb با روش آلياژ سازي مكانيكي

چكيده انگليسي :

Development of Nanostructured Intermetallic Compounds and Composites inNi Ti Nb Ternary System by Mechanical Alloying MarjanRahmdel m rahmdel@ma iut ac ir April11 2011 Department of Materials Engineering IsfahanUniversity of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiDr Mohammad Hassan Abbasi abbasi32@cc iut ac ir Supervisor Dr Mohammad Hosein Enayati ena78@cc iut ac ir Supervisor AbstractIn this investigation the synthesis of Ni50Ti 50 x Nbx x 5 10 25 nanostructured alloys Ni50Ti25Nb25 Al2O3nanostructured composites with 5 and 10 weight percent Al2O3 Ni50Ti25Nb25 Ni50Ti40Nb10 and Ni50Ti45Nb5stoichiometric nanostructured composites were studied by mechanical alloying The milling process was carriedout at room temperature in a planetary ball mill under Ar atmosphere X ray diffraction XRD scanningelectron microscopy SEM transmission electron microscopy TEM thermal analysis and microhardnessmeasurements were used to characterize the milled and heat treated powders The milled powder after 40 h wasannealed for 1 h at 900 C under argon atmosphere to investigate the phase transitions occurring duringannealing The hardness of powders was also determined by microhardness measurements using aVickersindentor at a load of 50 g and dwell time of 5 s Formation kinetics was also analyzed using Johnson Mehl Avrami JMA equation for Ni50Ti25Nb25 alloy Thermodynamic analysis of the process was also carried outusing Miedema model Kinetic analysis in Ni50Ti25Nb25 showed that reaction of solid solution formation isdiffusion controlled The results showed that mechanical alloying of Ni50Ti25Nb25 Ni50Ti40Nb10 and Ni50Ti45Nb5powder mixtures led to the formation of an amorphous phase At the early stages of MANi and Nb atoms weredissolved in Ti latticein Ni50Ti25Nb25 alloy Nb and Ti atoms dissolved in Ni lattice in Ni50Ti40Nb10andNi50Ti45Nb5alloys By further increasing the milling time nanocrystalline layers formed This structure causedenhancement of diffusion process in low temperatures and amorphous phase formation from kinetics viewpoint Heat treatment of amorphous phases gave rise to the formation of NiTi Ni3Ti and NiNb phases in the first alloy Ni3Ti NiTi2 and NiNb phases in the second alloy NiTi Ni3Ti and NiTi2 phases in the third alloy Thermodynamic investigation showed that the first phase formed in all of Ni50Ti 50 x Nbx alloys was solidsolution Mechanical alloying products in three alloys were in agreement with the results obtained frommiedema model NiO Ti Nb and Al powders were used as initial materials to manufacture stoichiometriccomposites Mechanochemical reaction between NiO and Al took place in a combustion mode The change inAl2O3weight percent led to change in reaction mechanism Nanocomposites with 5 and 10 weight percent Al2O3formed by a gradual mechanism because of the dilution effect of Ni Ti and Nb reaction between NiO and Aldelayed and Ni Ti and Nb formed an amorphous phase after 60 h of mechanical alloying and ultrafine Al2O3particles were dispersed in the amorphous phase The crystallite size of theAl2O3 phase which was formed bymechanochemical reaction was too small and further refinement occured with increasing MA time So that therewas not any trace of Al2O3 peaks in XRD pattern at 60 h MA Keywords Mechanical alloying Nanostructured materials Ni Ti Nb ternary alloys Intermetalliccompounds

رحم دل ، مرجان

توسعه تركيبات بين فلزي و كامپوزيت هاي نانو ساختار در سيستم سه تايي Ni-Ti-Nb با روش آلياژ سازي مكانيكي