425 AZ61マグネシウム合金押出材の疲労メカニズム(軽量化・高強度化材料(1))

抄録

Fatigue strengths of extruded AZ61 magnesium alloy plate in three different directions were investigated. Specimens were machined that the extrusion direction was parallel, perpendicular or 45-degree to the loading axis direction. Fatigue limit for the longitudinal, transverse and 45-degree specimens were 85, 63 and 67 MPa, respectively. Fatigue crack was nucleated from inclusions in the early stage of fatigue life for all three kinds of specimens. Fatigue crack growth behaviors of short and long cracks vere also investigated by using SECT and CT specimens, respectively. The results for short crack growth behaviors show that, transverse and 45-degree specimens exhibited higher fatigue crack growth rates compare to the longitudinal specimen. Fatigue crack growth curves arranged by effective stress intensity factor of all three directions for short crack coincide with those for long crack.