Alüminyum köpük malzemelerin toz metalürjisi yöntemi ile üretiminde üretim parametrelerinin malzemenin işlenebilirliği üzerindeki etkilerinin incelenmesi
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Date
2014-05
Authors
Ensarioğlu, Cihat
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Publisher
Uludağ Üniversitesi
Abstract
Kapalı hücreli alüminyum köpük malzemeler; mukavemet/ağırlık oranlarının, bası yükleri karşısında mekanik enerji emme kabiliyetlerinin, ses ve ısı yalıtım kapasitelerinin, (polimerik köpük gibi malzemelere göre) ergime sıcaklıklarının, geri-dönüşüm oranlarının yüksek olması nedeniyle bilimsel ve teknolojik (ticari-askeri) alanda dikkat çeken yeni nesil malzemelerdir. Bu çalışmada, toz metalürjisi yöntemiyle üretilen alaşımlı alüminyum köpüklerin (850 ve 7075) köpürme ve talaşlı imalat süreçleri araştırılmıştır. Köpürtme çalışmalarında, matris malzemenin benzetimli analizine dayanan kısımda, JMatPro ile, ergime-katılaşma aşamaları analiz edilmiştir. Köpürme ile ilgili deneysel kısımda, ilk olarak üretim faktörlerinin, malzemenin özelliklerini etkileyen ve bir kısmı görüntü analizi ile (ImageTool ile) bulunan şekilsel karakteristiklere (genleşme oranı, ortalama hücre alanı, dairesellik, kesit homojenliği) olan etkisi incelenmiş ve optimize edilmiştir. İkinci olarak ise, alaşım elementlerinin genleşme oranı ve kesit homojenliğine etkisi belirlenmiştir. Köpürtmede, Minitab ile yapılan deneysel tasarımlar (Taguchi, yanıt yüzey metodu -RSM-, karışım) kullanılmış ve sonuçlar bu programla analiz edilmiştir. Köpüklerin; XRD niteliksel faz analizi, SEM-EDX haritalama, SEM görüntüleme, mikro-sertlik ölçüm işlemleri yapılmıştır. Talaşlı imalat çalışmalarında; ilk olarak bazı kesme faktörlerinin (kesici takım tipi, kesme hızı, diş başına ilerleme) çeşitli değerleri denenmiş, ikinci olarak ise malzemenin alaşım oranları değiştirilerek denemeler yapılmış; işlenebilirliğin niteliksel değişimi (iş-parçasında sıvanma, takımda sıvanma, takım aşınması) araştırılmıştır. Taguchi deneylerinde, 7075 ve 850 için; köpürtücü madde yüzdesi, ikinci sıkıştırma basıncı, genleştirme sıcaklık ve süresi en önemli faktörler olmuştur. 850 için, fırın ilk sıcaklığının düşük olması, makro-yapıyı iyileştirmiştir. 7075 için, kalite karakteristiklerinin istenen seviyelerine ait köpürtme faktörleri değerlerini tavsiye edecek ve köpürtücü madde yüzdesini düşürmek için de kullanılabilecek doğrusal bir model RSM ile elde edilmiştir. 850 için (benzetimli faz analiziyle de yorumlanabilecek şekilde); bakırın, genleşme oranı, nikelin ise kesit homojenliği anlamında belirleyici olduğu görülmüştür. XRD, SEM, SEM-EDX haritalama analizlerinde, suda soğutulmuş olsa da 850 referanslı alaşımlarda CuAl2 fazına rastlamıştır. 850 referanslı alaşımlarda mikro-sertlik 40-60 HV0,1 çıkmıştır. Talaşlı imalat deneylerinde; kesme hızının artmasının serbest yüzeydeki talaş yapışmalarını artırdığı, ilerlemedeki artışın ise azalttığı görülmüştür. Tüm alaşımlar için, iş-parçasında gözle görülür bir sıvanma gerçekleşmemiştir.
Closed cell aluminum foams are new generation materials that are attractive to scientific community and technological applications (commercial-military) because of their high degrees of strength-to-weight ratio, ability to absorb mechanical energy, capacity of sound and heat insulation, melting temperature (with respect to materials like polymeric foams), recycling ratio. In this study, foaming and machining of alloyed aluminum foams (850 and 7075) produced by powder metallurgy route were investigated. On foaming studies, in the section in which the simulation of matrix material was performed, JMatPro was employed to analyze the melting-solidification stages. In experimental section, first, the effect of manufacturing factors on morphological characteristics (expansion ratio, average cell area, circularity, section homogeneity), which affects material properties and some of which were found by image analysis (with ImageTool), were examined and optimized. Secondly, the effect of alloying elements on expansion ratio and section homogeneity was determined. In foaming, Minitab was utilized when designing the experiments (Taguchi, response surface methodology -RSM-, mixture) and analyzing the results. The foams were subjected to XRD qualitative phase analysis, SEM-EDX mapping, SEM imaging, micro-hardness measurement. On machining studies; first, some machining factors (cutting tool type, cutting speed, feed per tooth) were examined, secondly, trials were made with varying alloying elements ratios; and machinability was interpreted in a qualitative manner (smearing on workpiece and tool, tool wear). In Taguchi experiments, for 7075 and 850; the most important factors were revealed as blowing agent percentage, secondary consolidation pressure, expansion temperature and time. For 850, the lower the initial furnace temperature the better the macro-structure was. For 7075, a linear model was obtained with RSM, with which foaming factor value recommendations for desired levels of quality characteristics can be drawn and also reductions on foaming agent percentage can be generated. For 850 (in a way that it can also be interpreted by phase simulation analyses); it was observed that Cu is the key element for expansion ratio and Ni was for section homogeneity. In 850-referenced alloys, phases of CuAl2 were encountered in XRD, SEM, SEM-EDX mapping analyses although the workpieces were water-cooled. The micro-hardness values for 850-referenced alloys were 40-60 HV0,1. In machining experiments; it was seen that increased cutting speed enhanced the chip smearing on tool flank face, while increased feed decreased it. For all the alloys studied, no smearing on workpiece was observed.
Closed cell aluminum foams are new generation materials that are attractive to scientific community and technological applications (commercial-military) because of their high degrees of strength-to-weight ratio, ability to absorb mechanical energy, capacity of sound and heat insulation, melting temperature (with respect to materials like polymeric foams), recycling ratio. In this study, foaming and machining of alloyed aluminum foams (850 and 7075) produced by powder metallurgy route were investigated. On foaming studies, in the section in which the simulation of matrix material was performed, JMatPro was employed to analyze the melting-solidification stages. In experimental section, first, the effect of manufacturing factors on morphological characteristics (expansion ratio, average cell area, circularity, section homogeneity), which affects material properties and some of which were found by image analysis (with ImageTool), were examined and optimized. Secondly, the effect of alloying elements on expansion ratio and section homogeneity was determined. In foaming, Minitab was utilized when designing the experiments (Taguchi, response surface methodology -RSM-, mixture) and analyzing the results. The foams were subjected to XRD qualitative phase analysis, SEM-EDX mapping, SEM imaging, micro-hardness measurement. On machining studies; first, some machining factors (cutting tool type, cutting speed, feed per tooth) were examined, secondly, trials were made with varying alloying elements ratios; and machinability was interpreted in a qualitative manner (smearing on workpiece and tool, tool wear). In Taguchi experiments, for 7075 and 850; the most important factors were revealed as blowing agent percentage, secondary consolidation pressure, expansion temperature and time. For 850, the lower the initial furnace temperature the better the macro-structure was. For 7075, a linear model was obtained with RSM, with which foaming factor value recommendations for desired levels of quality characteristics can be drawn and also reductions on foaming agent percentage can be generated. For 850 (in a way that it can also be interpreted by phase simulation analyses); it was observed that Cu is the key element for expansion ratio and Ni was for section homogeneity. In 850-referenced alloys, phases of CuAl2 were encountered in XRD, SEM, SEM-EDX mapping analyses although the workpieces were water-cooled. The micro-hardness values for 850-referenced alloys were 40-60 HV0,1. In machining experiments; it was seen that increased cutting speed enhanced the chip smearing on tool flank face, while increased feed decreased it. For all the alloys studied, no smearing on workpiece was observed.
Description
Keywords
Alaşımlı alüminyum köpükler, Alaşım elementleri, Deney tasarımı, Benzetimli faz analizi, Köpürtme, İşlenebilirlik, Alloyed aluminum foams, Alloying elements, Experimental design, Phase analysis simulation, Foamability, Machinability
Citation
Cihat, E. (2014). Alüminyum köpük malzemelerin toz metalürjisi yöntemi ile üretiminde üretim parametrelerinin malzemenin işlenebilirliği üzerindeki etkilerinin incelenmesi. Yayınlanmamış yüksek lisans tezi. Uludağ Üniversitesi Fen Bilimleri Enstitüsü.