Initiation of fatigue cracks in AZ91 Mg alloy processed by ECAP

0434745 - ÚFM 2015 RIV GB eng C - Conference Paper (international conference)
Fintová, S. - Kunz, Ludvík
Initiation of fatigue cracks in AZ91 Mg alloy processed by ECAP.
NANOSPD 6. Bristol: IOP Publishing Ltd, 2014 - (Benoît, B.; Olivier, B.; Emmanuel, B.; Thierry, G.), Art. n. 012159. IOP Conference Series: Materials Science and Engineering, 63. ISSN 1757-8981.
[NanoSPD6 - International Conference on Nanomaterials by Severe Plastic Deformation /6./ (30.06.2014-04.07.2014 : Metz). Metz (FR), 30.06.2014-04.07.2014]
R&D Projects: GA ČR GAP108/10/2001
Institutional support: RVO:68081723
Keywords : AZ91 magnesium alloy * ECAP * fatigue * crack initiation
Subject RIV: JL - Materials Fatigue, Friction Mechanics
http://iopscience.iop.org/1757-899X/63/1

Mechanism of fatigue crack initiation was investigated in ultrafine-grained (UFG) magnesium alloy AZ91 processed by equal channel angular pressing (ECAP). Fatigue behaviour of UFG material was compared to the behaviour of material in an initial as-cast state. Focused ion beam technique (FIB) was applied to reveal the surface relief and early fatigue cracks. Two substantially different mechanisms of crack initiation were observed in UFG structure, which can be characterized as bimodal even after 6 ECAP passes by route Bc. The bimodality consists in a coexistence of very fine grained areas with higher content of Mg17Al12 particles and areas exhibiting somewhat larger grains and lower density of particles. The fatigue cracks which initiate in areas of larger grains are related to the cyclic slip bands; this initiation mechanism is similar to that observed in cast alloy. The second initiation mechanism is related to the grain boundary cracking which takes place predominantly in the fine grained areas.
Permanent Link: http://hdl.handle.net/11104/0240010