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CYCLIC FATIGUE RESISTANCE OF AZ91 MAGNESIUM ALLOY

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Author(s): Aneta Němcová | Josef Zapletal | Martin Juliš | Tomáš Podrábský

Journal: Materials Engineering
ISSN 1335-0803

Volume: 16;
Issue: 4;
Start page: 5;
Date: 2009;
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Keywords: Magnesium alloy | Solution annealing | Mechanical properties | Fatigue properties | Fractography

ABSTRACT
The paper deals with determination of principal mechanical properties and the investigation of fatigue behaviour of AZ91 magnesium alloy. The experimental material was made by squeeze casting technique and heat treated to obtain T4 state (solution annealing), when hard, brittle Mg17Al12 intermetallic phase is dissolved. The basic mechanical properties (Young’s modulus, ultimate tensile strength, yield strength, elongation to fracture and reduction of area) were determined by static tensile test. Furthermore, fatigue parameters were investigated. The S-N curve on the basis of smooth test bars tested under symmetrical push-pull loading at room temperature was evaluated. The measured data were subsequently used for fitting with suitable regression functions (Kohout & Věchet and Stromeyer) for determination of the fatigue parameters. Fatigue limit sigma-c of the studied alloy for 108 cycles is approaching 50 MPa. In addition, the fracture surfaces were observed by scanning electron microscopy. The failure analysis proved that the striations were observed in fatigue crack propagation area and in the area of static fracture was observed the transgranular ductile fracture. The structure of the studied alloy in the basic state and after heat treatment was observed by light and scanning electron microscopy.
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