JSC “Alcoa SMZ”, Moscow, Russia:

A. M. Drits, Head of Moscow Office, Director of Business and New Technologies Department, e-mail: Alexander.Drits@alcoa.com
V. N. Nuzhdin, New Technology Manager

Moscow State Industrial University, Moscow, Russia:
V. V. Ovchinnikov, Professor of a Chair of Materials Science and Nano technologies

Railway Research Institute, Moscow, Russia:
A. D. Konyukhov, Leading Researcher

This article discusses the results of tensile and fatigue tests of base materials and welds of 1565ch (1565ч) alloy sheet. The fatigue tests were carried out at three stress ratios (R = –1.0; 0.1 and 0.5) in order to meet the EN 13981 requirements for aluminum alloys used in structural railway applications. Tested samples were prepared in accordance with the EN 10002-1 and EN ISO 6892-1 (B) requirements. Metal inert gas welding of the samples was carried out per EN ISO 14175. The fatigue tests at three stress ratios were carried out using repeated alternate tensile-compression load method. The fatigue resistance values were determined by the Wöhler regression method. Compensating logarithmic trendlines were drawn through the cloud of points resulting from the presentation of the magnitude of cyclical stress (So) vs. the logarithmic scale of cycles to failure (N) at the probability of survival P = 50%. It was confirmed that the level of mechanical properties of 1565ch alloy is by 15–20% higher in comparison with the properties of other high-magnesium aluminum alloys AMg5 (АМг5) and AMg6 (АМг6). All the stress ratios used in the research have determined that the fatigue test values of both base 1565ch material and its welds is always higher than the values set as the minimum allowable in the EN 13981. The influence of the welds porosity on fatigue resistance was studied. The mechanisms and the factors inducing weld seam porosity were defined: quantity of molecular hydrogen in the melted metal of the weld pool and duration of melted state of the metal. It was proved that the quality of welding significantly affects fatigue properties of the welds made of 1565ch alloy: porosity of the welding seam might decrease the threshold fatigue strength based on 107 cycles up to 30%.

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