Dresden 2014 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 34: Poster Session
MM 34.7: Poster
Dienstag, 1. April 2014, 18:00–20:00, P4
Influence of different loading stresses to duplex steel in the VHCF regime — •Anne Hüsecken1, Marcus Söker2, Konstantin Istomin1, Benjamin Dönges1, and Ullrich Pietsch1 — 1Universität Siegen — 2Hochschule Osnabrück
Damage mechanisms in the VHCF regime are still not sufficiently understood. Experiments on austenitic-ferritic duplex steels up to 109 cycles have revealed that elastic anisotropy causes stress concentrations at grain and phase boundaries leading to slip band emanation preferentially in the fcc austenite phase [1]. Slip bands raise locally the residual stress level in the neighbouring bcc ferrite grains. So, crack initiation along pronounced slip bands and grain/phase boundaries were observed [1,2]. There is a need to analyse the development of dislocations and their formation to slip bands within the grains in order to correlate the observed microstructure with relevant damage mechanisms. We present a new way of fatique analysis measuring the change of shape of selected austenite and ferrite X-ray Bragg reflections for single grains as function of the number of VHCF cycles and different loading stresses in-situ. It was explored that selected austenite reflections show an increasing peak splitting as function of load cycles whereas ferrite reflection kept nearly unchanged. This finding can be attributed to the formation of stress induced dislocations bunches in austenite grains which may acts as nuclei for crack formation in neighboured ferrite grains [3]. [1] U. Krupp: Fatigue Crack Propagation in Metals and Alloys (Wiley, 2007). [2] H. Knobbe et al, J. Phys.: Conf. Ser. 240 (2010) 012061 [3] K.Istomin et .al. Fatique, submitted 2013