摩擦攪拌接合したアルミニウム合金の疲労強度および塩水中での機械的性質に及ぼすTi-FPB処理の効果

摘要

This study was conducted to investigate the effects of titanium-fine-particle bombarding (Ti-FPB) treatment on fatigue strength of friction-stir-welded aluminum alloy (FSW material) and on its mechanical properties in salt water environment. Fatigue cracks of Ti-FPBed FSW material were initiated from the root of the overhung weld toes formed by the passing of the tool, as well as those of FSW material. Ti-FPB treatment introduced compressive residuals stress to the surface of FSW material, although its absolute value was relatively low near the weld toes. As a result, fatigue strength of FSW material was recovered by Ti-FPB treatment to the same level of the substrate. Ti-FPB treatment diffused titanium to the surface of FSW material. Diffusion of titanium was insufficient near the weld toes because of disturbance by the overhung weld toes. Such insufficient diffusion of titanium induced electrolytic corrosion. As a result, tensile strength of FSW material in salt water environment deteriorated with Ti-FPB treatment.%摩擦攪拌接合(friction stir welding,以後FSW)は，1991年に英国TWI(the Welding Institute)によって開発された固相接合法である.FSWは，プローブとショルダーから構成される回転ツールを板材の突合せ部に沿って移動させることにより，材料を攪拌させて接合する方法である.この方法を用いれば，アルミニウム合金やマグネシウム合金などの低融点金属を，高い強度水準を保ちながら比較的簡便に接合できる.