微細結晶粒を持つMg-Al-Zn系Mg合金の摩擦攪拌接合継手強度に及ぼすツール形状の影響

Friction stir welding was applied to join a fine-grained high tensile strength AZ31 alloy and a commercially extruded AZ31 alloy, and the effect of tool shape on the joint strength of the two magnesium alloys was investigated. For the commercially extruded AZ31 alloy with mean grain size of ca. 11 μm, the tool shape has almost no influence on the joint strength; for the fine-grained AZ31 alloy with mean grain size of ca. 1.9 μm, however, the joint strength was strongly influenced by the tool shape. The joint strength of the fine-grained AZ31 alloy increases with the ratio of shoulder diameter to probe diameter. It is found that the texture in the stir zone changes with the tool shape, which is one of the predominant factors controlling the joint strength of the fine-grained AZ31 alloy.