4874

4578

كارشناسي ارشد

ريخته گري

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مواد

1388

ده،149ص.: مصور،جدول،عكس،نمودار

ص.ع.به فارسي و انگليسي

بهزاد نيرومند

احمد كرمانپور

9/10/88

محمود مرآتيان،رحمت ا... عمادي

مهندسي مواد

ID4578

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

A new criterion for prediction of hot tearing tendency of cast alloys and its validation using A206 alloy Mohamad Reza Nasresfahani mr nasr2001@ma iut ac ir Date of Submission 2009 05 30 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Behazad Niroumand behzn@cc iut ac irAbstractHot tearing is a common defect which occurs during solidification of cast alloys with large mushy zones Determination of hot tearing tendency and the effective parameters are of great interest to researchers in thisfiled In the present research a two step process for determination of hot tearing tendency is introduced Thefirst step includes the design and manufacture of an apparatus for measuring the required physical andmechanical data needed in the second step The second step is utilization of a new proposed hot tearingcriterion named NNC which incorporates both mechanical and metallurgical parameters NNC wasvalidated using A206 aluminum alloy a very hot tearing prone alloy through changing such castingparameters as super heat temperature with and without grain refinement percentage of grain refiner copper and gas content of the melt The results were analyzed by NNC load rate and Davies criteria Theresults showed that NNC could more consistently predict the experimental results obtained and had higherprecision than other criteria This seems to be due to simultaneous utilization of both mechanical andmetallurgical parameters by NNC which enables it to give a more realistic picture of the concurrent effectsof several variables The results also showed that the hot tearing tendency of A206 alloy increases with anincrease in melt super heat Although addition of grain refiner at high super heat could not effectivelyrefine the microstructures it decreased the hot tearing tendency by slightly changing the grainsmorphology The optimum percentage of grain refiner for reducing hot tearing was recognized to be 1 Increasing copper content from 4 45 to 5 1 reduced hot tearing tendency Furthermore hot tearingtendency was increased by degassing because of increased contraction and reduced feed ability of the melt Key words Hot tearing susceptibility NNC A206 Supper heat Grain refinement Cupper content Degassing

بهزاد نيرومند

احمد كرمانپور

محمود مرآتيان،رحمت ا... عمادي