10575

9758

كارشناسي ارشد

شناسايي و انتخاب و روش توليد مواد مهندسي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مهندسي مواد

1394

دوازده، 80ص.: مصور

احمد كرمانپور، رحمت اله عمادي

1394/08/09

فتح اله كريم زاده، احمد رضائيان

1396/10/05

كتابنامه

مواد

مهندسي مواد

ID9758

Evaluating the Effect of Thermo mechanical Processing on Microstructure Mechanical Properties and Shape Memory Behavior of a TiNiCu Shape Memory Alloy Majid Abbasi Majid abbasi@ma iut ac ir 27 July 2015 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language PersianSupervisors Dr A Kermanpur Prof Email ahmad k@cc iut ac irDr R Emadi Assoc Prof Email remadi@cc iut ac irAbstract The shape memory effect is called to the ability to recovering the initial shape of a plastically deformed sample during athermo mechanical cycle Recently TiNi based ternary alloys such as TiNiNb and TiNiCu have been increasinglyconsidered Copper is one of the important alloying elements which affects phase transformation temperatures andreduces hysteresis On the other hand it is reported that grain refinement in shape memory alloys could optimizemechanical properties and shape memory behavior The main purpose of this research is to manufacture and characterizethe nanostructured shape memory Ti50Ni45Cu5 alloy by cold rolling annealing process Several samples of the alloy wereproduced by a copper boat vacuum induction melting process The as cast samples were homogenized and hot rolled at900 The hot rolled samples were then cold rolled up to 70 thickness reduction Finally the samples were annealed at400 about 1 hr Microstructural and phase evolutions were conducted by optical and electron microscopy X raydiffraction and thermal analysis techniques Mechanical properties and shape memory behaviors were evaluated usingtensile bending and hardness test methods According to the results of metallography thermal analysis and x raydiffraction tests the samples with the thickness reduction of higher than 50 had a bimodal structure a matrix withNano grains of austenite along with the amorphous structure in shear bands According to XRD and thermal analysisresults there was no amorphous structure shear band in the annealed samples During the annealing process recrystallization and crystallization of the amorphous structures occurred together The amorphous structure in shearbands is supposed to change to the Nano sized grains By increasing cold rolling from 20 to 70 the strength of samplesbecame about twice the shape recovery percentage increased from 86 to about 100 and the critical temperatures weredecreased about 20 It is thought that the reason behind these variations is grain refinement Grain refinement maycause twinning to be the predominant deformation mechanism enhancing the shape memory effect Mechanicalproperties of the Ti50Ni45Cu5 alloy were also changed in comparison to the TiNi alloy The tensile strength of theTi50Ni45Cu5 alloy was increased up to 500 MPa but hardness was decreased about 35 HV the critical temperatures werealso decreased about 20 This work clearly showed that thermo mechanical processing of cold rolling annealing couldimprove mechanical and shape memory properties of the Ti50Ni45Cu5 alloy Keywords TiNiCu Shape memory effect Superelasticity Thermomechanical processing Nano grainedstructure

احمد كرمانپور، رحمت اله عمادي

فتح اله كريم زاده، احمد رضائيان