AFMを用いたマグネシウム合金（AZ31）の微小疲労き裂発生および伝ぱ挙動の観察

抄録

In the present study, slip band formation and fatigue crack initiation in magnesium alloy (AZ31) were examined by means of atomic force microscopy (AFM). Plane bending fatigue tests were performed using computer-controlled electro-dynamic fatigue testing machine under a stress ratio of -1 in ambient laboratory atmosphere. Based on the replica method, replicas of the specimen surface were observed to examine the fatigue crack propagation. The crack initiation site on the specimen surface was identified by comparing the crack propagation and observing fracture surface. Result of fatigue tests, fatigue strength at 107 cycles of magnesium alloy was found to be about 92 MPa. It was seen many slip lines with various angles. In any cross-sectional shape, extrusion of slip bands in the vicinity of the crack was observed. Main crack shape during 6000 and 8000 cycles was curved, then the crack straightly propagated. It was found that crack propagation behavior depended on the stress intensity factor range ΔK. The main crack propagated even at very low stress intensity factor range.