Date of Award


Degree Type


Degree Name

Master of Applied Science (MASc)


Materials Science and Engineering


Marek Niewczas




Wrought AZ80 magnesium alloy from a spoke of forged automotive wheel was subjected to high cycle fatigue to study its fatigue properties and to understand the relationship between the material substructure and fatigue life. The results reveal that in axial tension-compression S-N testing the spoke material exhibits an endurance limit of 98MPa and a sharp bend in the S-N curve. Fracture surface observation by SEM revealed rapid crack growth after crack nucleation with micro voids and angled secondary cracks throughout. XRD analysis revealed a strong material texture beneficial to basal slip activation before and after fatiguing, with small amounts of refinement after cycling and no signs of twinning. TEM observations of samples cycled at high stress and stresses above and below the endurance limit revealed a large difference in the dislocation substructures developed, which may relate to the sharp bend in the S-N curve.

McMaster University Library

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