Multiaxial Fatigue Behaviour (HCF and LCF) of AZ31 Magnesium Alloy.

ABSTRACT. Nowadays in the automotive and aerospace industry, the improvement on fuel consumption and inherent vehicle performance has been an economical approach and a driving force from the customer side; moreover the fuel consumption reduction is also motivated by legislative rules to reduce primary energy consumption and environmental impact. In this context, magnesium alloys have been used to replace heavier structural materials such as steel and aluminium alloys; however exists a lack of information on the mechanical behaviour on magnesium alloys, in particular under multiaxial fatigue conditions. In this paper investigations were carried out to characterize the wrought magnesium alloy AZ31B-F behaviour in high and low cycle fatigue. Monotonic and cyclic mechanical properties were determined by tests on cylindrical specimens, moreover the multiaxial fatigue tests were performed with hourglass shape specimens. All specimens were machined from extruded rods. Four loading paths were considered; proportional, 90º out-of-phase and two uniaxial cases with R=-1 in tension and torsion. For each loading path a SN curve was determined. Under tension-compression tests, was found that the AZ31 magnesium alloy has a different mechanical behavior. Two different cyclic yield stress, one for tension, other for compression were determined. Furthermore, in high cycle fatigue regime it was observed that for the same equivalent stress the loading path type has a significant influence in the AZ31B-F fatigue strength