Tensile and fatigue properties of extruded AZ61 magnesium alloy plate in different orientations of basal plane to the principal stress axis were investigated in a controlled air (20 -55%RH). A sinusoidal loading form with a stress ratio R=0.1 and a frequency of 20Hz was applied to the fatigue specimens. The specimen in 45 degree direction from the extruded direction showed lower tensile strength compared to those in the longitudinal and transverse directions, while it demonstrated the highest elongation. Fatigue strength of the specimen in the longitudinal direction was higher compared to those for the specimens in the transverse and 45 degree directions. Inclusions served as a fatigue crack initiation site for all specimens regardless of specimen orientation. It is suggested that the dominant basal plane texture strongly affects the tensile and fatigue properties of extruded magnesium alloys.
Fracture strength and fracture behavior of sintered two-phase tungsten alloy specimens with various notch root radii were investigated. Cracks mainly initiated by interface decohesion between tungsten particles at the notch root. Cleavage fracture of tungsten particle was observed for the material with higher volume fraction of ductile matrix phase. No significant variation of crack initiation strength was found for notch root radii larger than 5mm. However, crack initiation strength significantly decreased with reducing notch root radii for the radii smaller than 5mm. The non-linear notch mechanics proposed by Nisitani et al has been successfully applied to the present materials.
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