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RISS 인기검색어
- 검색키워드
- 저자 : Amir Hossein Kokabi (검색결과 3 건)
- 무료
- 기관 내 무료
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Roll Bonding Behaviour of Al-3003/Al-4043 and Al-3003/Zn Sheets
Mojtaba Movahedi,Amir-Hossein Kokabi,Hamid-Reza Madaah-Hosseini,Mahdi Kiani 대한금속·재료학회 2011 METALS AND MATERIALS International Vol.17 No.4
In the present study, the roll bonding behaviour of Al-3003/Al-4043 and Al-3003/Zn sheets were compared. The bi-layer sheets were produced by a roll bonding process at different reductions in thickness and rolling temperatures. The joint strengths of the sheets were evaluated by peel and bend testing before and after supplemental annealing treatment. The peeled surfaces were examined using a scanning electron microscope. The results indicated that the Al-3003/Al-4043 sheets were bonded with higher joint strength and lower threshold reductions in thickness with respect to the Al-3003/Zn sheets. In contrast to the Al-3003/Zn sheets, significant improvement was observed in the joint strength of the Al-3003/Al-4043 sheets after annealing treatment. Moreover, electron microscopy examinations showed that the fracture types of the Al-3003/Al-4043 and Al-3003/Zn sheets were predominantly ductile and brittle, respectively.
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Microstructural Characteristics of a Cast IN718 Superalloy Bonded by Isothermal Solidification
Majid Pouranvari,Ali Ekrami,Amir-Hossein Kokabi,한흥남 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.5
Isothermal solidification is a key feature of transient liquid phase bonding which prevents the formation of deleterious intermetallic phases in the joint centerline and results in bonds with improved mechanical performance. This paper discusses the metallurgical characteristics and mechanical properties of an as-cast IN718 superalloy bonded by diffusion-induced isothermal solidification of Ni-7Cr-4.5Si-3.2B-3Fe (wt%)filler metal. After transient liquid phase bonding of as-cast IN718 at 1000 °C for 60 min, a bond exhibiting a solid solution microstructure with joint efficiency of 72% in terms of shear strength was obtained. The joining process was effectively able to prevent the formation of hard and brittle nickel and chromium borides, which typically lead to critical problems in brazing. The formation of Nb-rich Laves phase, which is well known as a major issue in the fusion welding of IN718, was not observed. The bonding time,which governs the extent of isothermal solidification, was a critical parameter for controlling the mechanical properties of the joints in terms of shear strength and hardness distribution across the bond.
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Abolfazl Fazaeli,Aliakbar Ekrami,Amir Hossein Kokabi 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5
In this research, production of ferrite - martensite dualphase Steels with different martensite morphology was considered during transient liquid phase bonding of a low carbon steel. The steel was bonded using an iron base interlayer with melting point of 1443 K and 40 μm thickness. Bonding process carried out at 1473 K, under pressure of 0.5MPa, at different holding time of 10, 20, 30 and 40 minutes. Microstructural studies of joint region showed that isothermal solidification completed at the bonding time of 40 minutes. Microstructure of joints made at the bonding time of 10, 20, and 30 minutes consists of two distinct region, athermal and isothermal solidified zones. Microstructure of these zones was studied and chemical composition of these zones was determined by EDS. Joints made with bonding time of 40 minutes were homogenized at 1008 K and then cooled into cold water to produce dual phase ferrite and martensite microstructure with different martensite morphology. According to shear test results, it was found that the shear strength of ferrite - fibrous martensite microstructure is greater than those with ferrite - continuous martensite and ferrite - blocky martensite microstructure.
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