Development of Selfoontrolling Friction Stir Welding for High Temperature Materials and Analysis of Micmsfructure Evolution during Friction Stir Welding

点击翻译按钮获取中文摘要

A new system was developed where the probe and the shoulder can individually rotate with the same rotation axis. Two 5mm aluminum alloys (1050 and 5083), 1.6mm IF and carbon steels, and 2mm commercially pure Ti were joined using this system. By changing the shoulder rotation speed between 0 and 1750rpm and the probe rotation speed between 0 and 1750rpm, the effects of rotation speeds of the shoulder and probe on the joint properties were clarified. As a result, it was found that under the conditions where no defect is formed, the rotation speed of the probe seldom influenced the strength of the joint, but the rotation speed of the shoulder significantly affected the joint strength. This indicates that the shoulder rather than the probe generates more heat. On the other hand, the formation of defects is significantly affected by the probe rotation speed, and at 250rpm or less, the defects are formed even when the rotation speed of the shoulder increases significantly.For Ti alloys which are suddenly softened in a certain temperature region, a stationary shoulder FSW is effective because the heat can be released from the shoulder as well as the heat input from the shoulder is restricted. The size, shape and orientation of the grains were analyzed in detail using TEM and EBSP, and it was found that the drop in the hardness in the stir zone can be decreased when only the rotating probe is used.addition, various tools were developed to use high melting point materials, and then the FSW of high melting point metals, such as steel material, nickel basis super alloy, Ti alloy, and pure Mo was succeeded. The melting point of pure Mo is 2620 degrees C, which is the world record at present.