Publication: Development of a novel severe plastic deformation method for a thin-walled open section beam : thin-walled open channel angular pressing (two-cap)
Abstract
Bu çalışmada, u-profil şeklinde numuneler için ince cidarlı açık kanal açısal presleme (İCA-KAP) olarak adlandırılan yeni bir aşırı plastik deformasyon (APD) metodu geliştirilmiştir. Böylece, APD metodu yardımıyla tane boyutu küçültülerek malzemenin özelliklerinin arttırılması amaçlanmıştır. Yeni geliştirilen yöntem ile AZ31, AA5083 alaşımları ve ticari saf bakır malzemeleri deneysel çalışmalarda kullanılmıştır. Çalışma kapsamında yöntemin ilkelerine uygun parametreler öncelikle belirlenmiş ve sistemin analitik modeli oluşturulmuştur, ardından çalışma nümerik analiz (sonlu elemanlar yöntemi) ile desteklenmiştir. Teorik çıktılar dikkate alınarak üretilen, İCA-KAP kalıpları ile uygun bir deney düzeneği kurulmuştur. Numuneler kalıp kanalına uyacak şekilde u-profil şeklinde, katı haldeki malzemelerden işlenerek üretilmiş ve tavlanarak İCA-KAP kalıp kanalı boyunca 4 geçişe kadar preslenmiştir. Deneysel çalışmaların ardından, mekanik ve mikroyapısal özelliklerdeki değişiklikleri belirlemek için numuneler test edildi. Bu aşamada mekanik özellikleri belirlemek için çekme testi ve sertlik testi uygulanırken, optik mikroskop, taramalı elektron mikroskobu, enerji dağılımlı spektroskopi, X-ışını kırınımı ve transmisyon elektron mikroskobu analizleri seçilmiş alan elektron difraksiyonu ile mikroyapısal gelişmeleri görmek için uygulanmıştır. Sonuç olarak, aşırı plastik deformasyonun etkisiyle malzemelerin mikroyapı ve tane boyutlarında değişiklikler meydana gelmiştir. Tavlanmış yapılara göre tane boyutu küçülerek daha uniform hale gelmiş ve bu sebeple; mukavemet, sertlik ve tokluk değerleri üzerinde iyileşme gözlenmiştir. Açık kesitli profiller, endüstrinin birçok alanında yaygın olarak kullanılmaktadır; özellikle otomotiv ve havacılık endüstrisinde yüksek mukavemet-ağırlık oranında sahip malzemelere ihtiyaç duyulmaktadır. Fakat, literatür incelemesinde bu tür profiller için geliştirilmiş herhangi bir APD metoduna rastlanmamıştır. Bu nedenle, yapılan tez çalışmasının orijinal bir çalışma sunarak malzeme geliştirme teknolojisi ve endüstrisi için yararlı olacağı beklenmektedir.
In this study, a novel severe plastic deformation method (SPD) is named as thin-walled open channel angular pressing (TWO-CAP) was developed for u-type cross-sectional specimens. Thus, it is aimed to increase the material properties by minimizing their grain size by the help of the SPD method. By the newly developed method, AZ31, AA5083 alloys and commercially pure copper materials were used in experimental studies. Within the scope of the study, firstly the parameters were determined by the principles of the method, and an analytical model of the system was generated, following that, the study was supported by the numerical analysis (finite element method). Then, a suitable experimental setup was established with TWO-CAP dies, which were produced by taking into account theoretical outputs.After that, the specimens were machined from bulk material in u-profile shape as to fit the die channel, and then these specimens were annealed and pressed along the channel of TWO-CAP die up to 4 passes. Then, the specimens were tested in order to determine the changes in mechanical and microstructural properties. In this stage, the tensile test and hardness test were applied to determine the mechanical properties while, optical microscope, scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction, and transmission electron microscope analyses with selected area electron diffraction were applied to see microstructural improvements. As a result, improvement on strength, hardness, and toughness were observed depending on the changes on the microstructures and grain sizes of materials due to the large plastic deformation. Open cross-section profiles are widely used in many areas of the industry; they are especially desired in high strength to weight ratio in the automotive and aerospace industry. However, any developed SPD study for these type profiles cannot be encountered in the literature. Thus, this thesis study presents an original study, and it is expected that it will be beneficial for material development technology and industry.
In this study, a novel severe plastic deformation method (SPD) is named as thin-walled open channel angular pressing (TWO-CAP) was developed for u-type cross-sectional specimens. Thus, it is aimed to increase the material properties by minimizing their grain size by the help of the SPD method. By the newly developed method, AZ31, AA5083 alloys and commercially pure copper materials were used in experimental studies. Within the scope of the study, firstly the parameters were determined by the principles of the method, and an analytical model of the system was generated, following that, the study was supported by the numerical analysis (finite element method). Then, a suitable experimental setup was established with TWO-CAP dies, which were produced by taking into account theoretical outputs.After that, the specimens were machined from bulk material in u-profile shape as to fit the die channel, and then these specimens were annealed and pressed along the channel of TWO-CAP die up to 4 passes. Then, the specimens were tested in order to determine the changes in mechanical and microstructural properties. In this stage, the tensile test and hardness test were applied to determine the mechanical properties while, optical microscope, scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction, and transmission electron microscope analyses with selected area electron diffraction were applied to see microstructural improvements. As a result, improvement on strength, hardness, and toughness were observed depending on the changes on the microstructures and grain sizes of materials due to the large plastic deformation. Open cross-section profiles are widely used in many areas of the industry; they are especially desired in high strength to weight ratio in the automotive and aerospace industry. However, any developed SPD study for these type profiles cannot be encountered in the literature. Thus, this thesis study presents an original study, and it is expected that it will be beneficial for material development technology and industry.