AA2024 alüminyum alaşımının tiksotropik yapısı üzerine sima yöntemindeki deformasyon oranının etkisi

Bu çalışmada, bir dövme alaşım olan AA2024 alaşımında gerinimin neden olduğu sıvı aktivasyonu (straininduced melt activated-SIMA) yöntemi ile yarı-katı şekillendirme için gerekli tiksotropik mikroyapı üretimiaraştırılmıştır. Bu amaçla ekstrüze halde AA2024 alaşımı değişik oranlarda soğuk deformasyona tabi tutulmuşve takiben yarı-katı bölgeye ısıtılarak oda sıcaklığına sahip suda soğutulmuştur. Mikroyapı analizlerimetalografik inceleme ve nicel ölçüm yöntemleri ile yapılmıştır. Deneysel sonuçlar, SIMA yöntemiyle AA2024alaşımında, yarı katı şekillendirme için gerekli olan küresel şekilli tiksotropik mikroyapıların üretilebileceğinigöstermiştir. Artan soğuk deformasyon oranı ile şekil faktörü artarken tane boyutu azalmıştır. SIMA yöntemi iletiksotropik yapı üretimi için en az %20 soğuk deformasyonun gerekli olduğu belirlenmiş ve tiksotropik yapıdönüşümü için yarı-katı sıcaklıkta izotermal bekletmeye gerek olmadığı tespit edilmiştir.

Effect of predeformation rate in sima process on thixotropic structure of AA2024 aluminium alloy

In this study, thixotropic microstructure produced in a wrought AA2024 alloy for the semi-solid forming wasinvestigated by strain induced melt activated (SIMA) method. For this purpose, AA2024 alloy as extruded statewere subjected to cold deformation at different rates, following heated to a semi-solid region, and cooled inwater at room temperature. Microstructure analysis was achieved by metallographic and quantitative methods.Experimental results showed that spherical shaped thixotropic microstructures which required for semi-solidforming can be produced in AA2024 Al alloy by SIMA process. With increasing cold deformation rate, theshape factor increases while the grain size decreased. For the production of thixotropic structure by SIMAprocess, cold deformation rate was determined to be necessary at least 20%, and there is no need to isothermalholding at semi-solid temperature for thixotropic structure transformation.

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