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Hoppe C.,Technical And Macromolecular Chemuniversitat Paderbornwarburger Str 10033098Paderborngermany | Ebbert C.,Technical And Macromolecular Chemuniversitat Paderbornwarburger Str 10033098Paderborngermany | Voigt M.,Technical And Macromolecular Chemuniversitat Paderbornwarburger Str 10033098Paderborngermany | Schmidt H.C.,Forming And Machining Technologyuniversitat Paderbornwarburger Str 10033098Paderborngermany | And 4 more authors.
Advanced Engineering Materials | Year: 2016

Interface modification based on ultra-thin mercapto-propyl(trimethoxy)silane (MPTMS) films is shown to promote joining of copper and aluminum by plastic deformation followed by a heat treatment. The surface morphology and the surface chemistry of the metal substrates were analyzed by means of FE-SEM, XPS, and FT-IRRAS. The spectroscopic data show that the MPTMS film is crosslinked via Si-O-Si bonds and that stable Cu-S and Si-O-Al interfacial bonds are formed. The shear-force tests of the joints led to force displacement curves that are characteristic for a covalently bonded interface. Complementary cross sectional SEM and EDS analysis of the joint proved that a defect-free interface was formed without any measureable interdiffusion of metals across the interface or cracking of an oxide films. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Hordych I.,Institute For Werkstoffkunde Materials Science Leibniz University Hannoveran Der University 230823Garbsengermany | Rodman D.,Institute For Werkstoffkunde Materials Science Leibniz University Hannoveran Der University 230823Garbsengermany | Nurnberger F.,Institute For Werkstoffkunde Materials Science Leibniz University Hannoveran Der University 230823Garbsengermany | Hoppe C.,Technical And Macromolecular Chemuniversitat Paderbornwarburger Str 10033098Paderborngermany | And 4 more authors.
Steel Research International | Year: 2016

In the present study, the improvement of the bond strength of galvanized steel sheets in the cold roll bonding process is investigated. Zn-Fe intermetallic compounds are employed as an intermediate layer. The galvanized low-carbon steel is cold roll bonded. Prior to the roll bonding, the sheets are heat treated in the temperature range from 450 to 550°C. The influence of the heat treatment on the bond strength is investigated. It is found that the use of the pre-rolling annealing increases the bond strength. The highest average value is observed after a treatment at temperatures in the range from 450 to 500°C. Higher temperatures, however, reduce the bond strength. The bond is analyzed by optical and scanning electron microscopy (SEM) and evaluated in a tensile shear test. The interaction between iron and zinc is considered to be responsible for the improved bond strength. The presence of intermetallic compounds in the interface zone forms a brittle layer, which is required to create juvenile surfaces due to local fracturing during the roll bonding. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Besserer H.-B.,Institute For Werkstoffkunde Materials Science Leibniz University Hannoveran Der University 230823Garbsengermany | Dalinger A.,Institute For Werkstoffkunde Materials Science Leibniz University Hannoveran Der University 230823Garbsengermany | Rodman D.,Institute For Werkstoffkunde Materials Science Leibniz University Hannoveran Der University 230823Garbsengermany | Nurnberger F.,Institute For Werkstoffkunde Materials Science Leibniz University Hannoveran Der University 230823Garbsengermany | And 3 more authors.
Steel Research International | Year: 2016

In order to produce components with massive secondary functional elements from sheet metal bulk forming operations, termed sheet-bulk metal forming, can be applied. Owing to high, three-dimensional stress and strain states present during sheet-bulk metal forming, ductile damage occurs in the form of micro-voids. Depending on the material flow properties, tensile residual stresses can also be present in the components' formed functional elements. During service, the components are subjected to cyclic loading via these functional elements, and tensile residual stresses exert an unfavorable influence on crack initiation and crack growth, and therefore on the fatigue life. Following the forming process, temperature and microstructurally related compressive residual stresses can be induced by local heat treating of the surface. These residual stresses can counteract potential crack initiation on the surface or in the subsurface regions. In the present study, the adjustability of the residual stress state is investigated using a workpiece manufactured by orbital cold-forming, which possesses an accumulation of material in its edge region. Based on residual stress measurements in the workpiece's edge region using x-ray diffractometry, it is possible to verify the compressive residual stresses adjusted by varying the cooling conditions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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