5220

4890

كارشناسي ارشد

ريخته گري

اصفهان: دانشگاه صنعتي اصفهان،دانشكده مواد

1388

ده،103ص.:مصور،جدول،نمودار

ص.ع.به فارسي

بهزاد نيرومند

6/3/89

محمدحسين فتحي،رحمت ا...عمادي

مهندسي مواد

ID4890

به فارسي و انگليسي:قابل رويت در نسخه ديجيتالي

Squeeze casting of ductile iron and study of the effects of applied pressure on its microstructure and mechanical properties Hamid Khodaverdi h khodaverdi@ma iut ac ir Date of Submission 2010 03 14 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Behzad Niroumand behzn@cc iut ac irAbstractIn the present work the effects of applied pressure during solidification on microstructure and mechanicalproperties of a hypereutectic ductile iron were investigated The suitable chemical composition of the base castiron 3 65 wt C 2 24 wt Si and 4 4 wt C E to avoid excessive carbide formation in the microstructures wasdetermined after some preliminary test Also the close lid ladle nodulizing treatment was recognized as thesuitable nodulizing method for treating small quantities about 5Kg of cast iron Furthermore effects of someof the nodulizing treatment parameters on the microstructures were examined and 1400 C 3wt addition and20 seconds were chosen as suitable processing values for nodulizing temperature amount of nodulizing agentaddition and delay time between nodulization and pouring respectively Consequently magnesium treatedmelts were squeeze cast under external pressures of up to 75MPa using a hydraulic press and theirmicrostructural and mechanical characteristics were investigated Microstructural measurements were carriedout on un etched and etched surfaces of the castings using an optical microscope and Clemex image analysissoftware Results showed that pressurized solidification of ductile iron had a significant effect on itsmicrostructure and especially on the characteristics of the graphite nodules Increasing the applied pressure fromzero to 75Mpa decreased the amount of free graphite observed in the microstructures reduced the nodule sizeand increased the graphite nodule count and graphite nodules sphericity Increasing of the applied pressure alsoresulted in higher pearlite and cementite and lower ferrite contents in the microstructures Moreover theultimate strength yield strength and fracture toughness of the castings improved as the applied pressure rosefrom zero to 50MPa Further increase in the applied pressure resulted in slightly lower mechanical properties SEM fractographs showed an increasing trend for ductility of the fractured surface with increasing the appliedpressure up to 50MPa followed by a decrease as the pressure was further increased to 75MPa The reduction inthe mechanical properties at the highest applied pressures was associated with the influence of the appliedpressure on the formation of more carbide phase and decrease in the graphite nodule cont in the microstructures KeywordsSqueeze casting Ductile iron Solidification under pressure Microstructure Graphitenodules Mechanical properties

بهزاد نيرومند

محمدحسين فتحي،رحمت ا...عمادي