摩擦攪拌によるA6063/S45C突き合わせ接合体の疲労強度特性におよぼす時効処理の影響

抄録

The butt dissimilar joints of Al-Mg-Si alloy JIS A6063 and carbon steel JIS S45C by means of friction stir welding were prepared for investigating fatigue properties of the joints and also to investigate the effect of heat treatment on fatigue properties of the dissimilar joints. The heat treatment conditions were same condition as the artificial aging process for A6063. From the experimental results, there were some cases that the fatigue fracture mode was different by the difference of the joint. In case of the joint which some defects existed in the stir zone, fatigue fracture occurred at stir zone for non-heat treated specimen and occurred at interface between A6063 and S45C for heat treated specimen. In case of the joint which no defect found in the stir zone, fatigue fracture occurred at a boundary between lower hardness region and base metal or occurred at the interface for non-heat treated specimen. On the other hand, in the case of heat treated specimen, fatigue fracture occurred at lower hardness region for higher applied stress level and occurred at interface between A6063 and S45C in case of middle or lower applied stress level. For both case of the joint which some defects existed or which no defect existed, fatigue strength was improved approximately 25% by heat treatment, because the hardness recovered by the heat treatment where the fracture occurred in the case of non-heat treated specimen.