Bending behavior of nickel-coated aluminum alloy 6156-T61
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Research Letter
Bending behavior of nickel-coated aluminum alloy 6156-T61 C.N. Panagopoulos, Laboratory of Physical Metallurgy, National Technical University of Athens, Zografos, 15780, Athens, Greece K.I. Giannakopoulos, Strength of Materials Laboratory, Piraeus University of Applied Sciences, 250 Thivon & P. Ralli Str. 12244 Egaleo—Athens, Greece H.P. Kyriakopoulou, Laboratory of Physical Metallurgy, National Technical University of Athens, Zografos, 15780, Athens, Greece Address all correspondence to K.I. Giannakopoulos at [email protected] (Received 19 March 2018; accepted 10 July 2018)
Abstract This study constitutes an attempt to characterize the microscopic strain distribution during bending in the AI6156-T61 aged alloy and in the same aluminum alloy with nickel coating. Bendability was detected in both groups by load-displacement curves, at four different strain rates (0.5, 2, 5, and 10 mm/min). In the case of the bare aluminum alloy, the terminal bending angle (without fracture occurring) was 83°. It can be suggested that hemming effect, delamination, spallation, and falling back of the coating was evident in both regions. The surface morphology of the alloys under examination was studied using a scanning electron microscope connected to an energy-dispersive spectroscope.
Introduction The use of aluminum alloys has been considerably increased in automotive structural applications due to the fact that they have low density, good formability, and high strength. Bending is also highly important in the shaping of parts of great complexity. Several experimental studies have been conducted so as to examine the influence of alloy composition on the behavior of 6000 series alloy sheets under bending conditions.[1–4] The damage incurred in the process of bending tends to be attributed to developing surface roughness as well as to intense strain localization, with shear bands being initiated at sites of strain concentration due to variable initial thickness.[5–9] In all cases, the manufacturing of aluminum panels of optimal strength for use in the automotive industry depends on the chemical composition of the relevant alloys in conjunction with thermomechanical processes.[5,6] Davidkov et al.[10] studied the importance of Mg2Si and AlCuMgSi Q-phase particles in the bending behavior of the 6016 series aluminum alloy. They found that bendability decreased as copper, iron, and silicon content increased. Other studies have also examined the way in which thermal softening affects shear banding.[11,12] Nickel has been widely employed in the production of coatings designed to ameliorate the surface characteristics of Al alloys for use in microelectronic devices.[13–19] Nickel deposition can be achieved by electrolytic (galvanostatic as well as potentiostatic) and electroless techniques on zincate-coated aluminum alloys.[13–15,17,20–22] The present study focuses on the correlation between bendability and the microstructure of uncoated and Ni-coated AI6156 sheets at different strain rates. For the nickel coating on th
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