Investigation of the Hydrogen Embrittlement Susceptibility of AA5083-H111 and AA6082-T6 Dissimilar Friction Stir Welds
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JMEPEG https://doi.org/10.1007/s11665-019-04489-y
Investigation of the Hydrogen Embrittlement Susceptibility of AA5083-H111 and AA6082-T6 Dissimilar Friction Stir Welds H.P. Kyriakopoulou, C.N. Farantos, A. Vazdirvanidis, A.G. Markoulis, C.A. Xanthis, E.V. Chatzidouros, and D.I. Pantelis (Submitted May 20, 2019; in revised form October 31, 2019) The present study focused on the evaluation of the hydrogen embrittlement susceptibility of dissimilar friction stir welds of AA5083-H111 and AA6082-T6 aluminum alloys. Electrochemical cathodic charging and slow strain rate tensile method were performed to investigate the embrittlement effect of diffused hydrogen cations into the polycrystalline matrices. The main embrittlement mechanisms were studied for applied current densities of 20, 50 and 80 mA/cm2 and duration of cathodic charging effect for 2 and 4 h. The slow strain rate tensile tests were performed with a strain rate of 2.4 3 10–4 s21 in order to promote hydrogen migration effect to critical sites (deep traps). With the increment in applied current density from 20 to 80 mA/cm2, a severe reduction in ductility and a lower decrease in yield stress and ultimate tensile strength were observed. The fractured surfaces were characterized by increased volume fraction of embrittling features such as river patterns, quasi-cleavage facets and teardrop ridges. Keywords
dissimilar metals, fracture analysis, friction stir welding, hydrogen embrittlement
1. Introduction The absorption and diffusion of hydrogen within the matrices of metallic materials have been known for many decades to have a detrimental effect on their microstructural characteristics and to provoke severe degradation of their mechanical properties. This phenomenon is referred to (Ref 1, 2) literature as hydrogen embrittlement (HE), and it is considered to be responsible for the premature failure of many alloy systems, particularly steel and aluminum alloys, which are the most widely used ones (Ref 1). In many cases, the catastrophic failure of the metal structures, which manifested at much lower applied load and far earlier than expected under normal conditions (without the presence of dissolved hydrogen in the crystalline structure), has been attributed to the occurrence of the hydrogen embrittlement phenomenon. Due to the significant hydrogen embrittlement susceptibility of steel and aluminum alloys and their widespread and constantly increasing use in a variety of industrial applications, a great number of hydrogen-related failures have been reported in the past several years, resulting in significant financial costs for repair processes or even complete destruction of the metal structures. However,
H.P. Kyriakopoulou, C.N. Farantos, A.G. Markoulis, C.A. Xanthis, and D.I. Pantelis, Shipbuilding Technology Laboratory, School of Naval Architecture and Marine Engineering, National Technical University of Athens, Athens, Greece; A. Vazdirvanidis, Metallography and Electron Optics Department, ELKEME - Hellenic Research Centre for Metals S.A., Oinofyta, Greece;
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