شكل ريزي نيمه جامد آلياژ A356 به روش SSR و مشخصه يابي نمونه هاي توليدي

چكيده انگليسي :

Rheocasting of A356 Alloy by SSR Process and Characterization of the Produced Samples Mir Taher Seiyedbeigi mirtaher@ma iut ac ir May 20 2009 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Behzad Niroumand behzn@cc iut ac ir Abstract Semi Solid metal SSM processing has been introduced as a rather new near net shape manufacturing method duo to its unique advantages relative to the conventional metal forming processes casting and forging Semi solid processing is typically classified into two major categories i e thixocasting and rheocasting In recent years a number of new rheocasting termed Slurry on Demand processes has been developed due to high cost of thixocasting routes Semi Solid Rheocasting SSR process is a novel SoD process developed at MIT that uses a combination of rapid local cooling and convection as the alloy cools through its liquidus to make a non dendritic semi solid slurry with good thixotropic behavior In this study a cup shaped SSR processed casting made from A356 alloy was produced in a squeeze casting die and its microstructural characteristics and mechanical properties were studied After some preliminary experiments to determine the SSR process parameters the effects of pouring temperature solid fraction and applied pressure on the surface quality casting density microstructure internal and external volumetric defects and mechanical properties of the produced components were investigated Six pouring temperatures of 645 and 700 C in the liquid state and 595 590 585 and 580 C in the semi solid state under 10 MPa external pressure and four external pressures of about 10 30 50 and 70 MPa at pouring temperature of 590 C were employed Results showed that the surface quality of the castings produced in semi solid state was rather poor relative to the castings poured from the liquid state Moreover with decreasing the pouring temperature increasing the solid fraction in semi solid state the surface quality of the castings was deteriorated This problem was diminished with applying a thicker die coating Densities of the components produced in semi solid state were more than the components formed in the liquid state and densities of components were increased with increasing the applied pressure Results indicated that with increase in the solid fraction roundness and average grain size of primary solid particles increased It was observed that the solid fraction of the primary particles at the bottom of the castings was more than other points due to the liquid segregation This phenomenon was studied in various solid fractions and a model was suggested to explain the occurrence of liquid segregation during squeeze casting process The shrinkage defects observed in fully liquid cast components were eliminated in SSR cast ones Furthermore the results showed that the mechanical properties of the castings were influenced by liquid segregation In conclusion low solid fraction slurries appeared more suitable for squeeze casting than high solid fraction slurries because of the better surface quality less liquid segregation and better mechanical properties of the castings Key words SSM SSR pouring temperature applied pressure liquid segregation A356 pdfMachine A pdf writer that produces quality PDF files with ease Produce quality PDF files in seconds and preserve the integrity of your original documents Compatible across nearly all Windows platforms simply open the document you want to convert click print select the Broadgun pdfMachine printer and that s it Get yours now

سيدبيگي، مير طاهر

شكل ريزي نيمه جامد آلياژ A356 به روش SSR و مشخصه يابي نمونه هاي توليدي

دماي ريخته گري , فشار اعمالي , جدايش مذاب , خواص مكانيكي