رابطه بين ساختار ميكروسكوپي و نحوه عملكرد آميژان Al-Ti-C در سرعت هاي انجماد مختلف

چكيده انگليسي :

Relationship between microstructure and performance of Al Ti C master alloy at different cooling rates Vahid Hassanbeygi v hassanbeygi@ma iut ac ir 4 July 2011 Department of Materials Engineering Isfahan University of Technology Isfahan Iran Degree M Sc Language PersianSupervisor A Shafyei Associate Professor Shafyei@cc iut ac irAbstractGrain refining process used in aluminum alloys has a significant role for preventing columnar coarse grains and encouraging fine grain formation Fine grained alloys have high strength goodtoughness fatigue resistance and high resistance to hot tearing In addition fine grains improve thesurface quality and reduce the need for machining That is the main reason for produce alloys withfine grain microstructure There are different methods for reducing grain size including thedynamic thermal and chemical methods In the most effective and widely used method a chemicalis added to molten alloy In the past decades Al Ti and Al Ti B grain refiners were used foraluminum alloys but in recent years because of weaknesses of these grain refiners a new grainrefiner in the form of Al Ti C master alloys was introduced In the other hand Although Al Ti Bmaster alloys are widely used as aluminum grain refiners but there are problems in theirapplication Because of great properties of Al Ti C refiners they can be considered as a suitablecandidate for use instead of Al Ti B master alloys In recent years Al Ti C refiners have attracteda huge attention among researchers In this study by addition of titanium and carbon powders withthe specified weight ratio to molten aluminum Al 3Ti 1C master alloy produced at 900 and 1200 C Because the microstructure and phases formed during the solidification are dependent on thecooling rate so master alloys produced at 900 C and 1200 C cooled at four different rates 1 1 9 4 and 7 C s By spectrometric analysis technique the recovery percent of the elements in themaster alloy is determined To identify the phases formed in grain refiner the X ray diffractionanalysis XRD was used The results clarified that the phases Al3Ti TiC and Ti6C3 75 are formed inmaster alloy Master alloy that produced at different cooling rates was added to the moltenaluminum at 720 C and fading time was studied The results show that grain refiner that solidifiedat 4 C s is more effective than other cooling rates On the other hand by reducing the cooling rate fading time of master alloy increased The results also showed that higher temperatures haveproduced long Al3Ti phase This phase have high fading time Adding different amount of grainrefiner to melt shows that best amount of grain refiner that produced at 900 C and 1200 C is 0 05wt and 0 2 wt respectively Also it was found that refining efficiency of master alloy thatproduced at 1200 C is more than other master alloy In this study by plotting cooling rate ofmaster alloys and aluminum two empirical correlations between cooling rate and grain size ofaluminum are proposed These correlations are applicable in a relatively wide range of coolingrates Key words Master alloy Grain refiner Fading time Grain refining efficiency

حسن بيگي، وحيد

رابطه بين ساختار ميكروسكوپي و نحوه عملكرد آميژان Al-Ti-C در سرعت هاي انجماد مختلف

جوانه زا , زمان ميرايي , قدرت ريز كنندگي