| The technology of Friction Stir Welding is a new, solid-state welding method. It has enabled us to butt-weld low fusibility alloys, such as aluminum alloys, which are often difficult to fusion weld, without voids, cracking, or distortion. However, the widely applied aluminum alloys is mostly joined in rivet joint or mechanical joint at present. It does not validly utilize the full properties of light mass and high strength in aluminum alloys. So it is very important to study the friction stir welding technology of aluminum alloys.Because the application time is not long, it is in the early stage to study the mechanic of friction stir welding. It is also not applied in our country. The core technology in friction stir welding is the special devised pin and the matched technology parameters, for it controls the application field in friction stir welding. To grasp the friction stir welding technology of aluminum alloys, and based on a sticky friction theory, the welding mechanism in friction stir welding is studied, and an energy model of friction stir welding is established, then the characters of thermal variance in friction stir welding is disclosed, and it is also disclosed that the thermal variant has an effect on the welding microstructure, and the peak temperature is an important parameter, for the reason that a good welding is gained when the peak temperature is kept about 0.8Tm (about 450癈). Finally, based on the above theoretical analysis, several kinds of special pin is designed, and by welding experiments for many kinds of aluminum alloys, some technology parameters for the select sharp-threw pin are obtained, and the influenceof the stirrer's shape, rotation speed, and welding speed etc on joint quality is studied. It has laid a theoretic and experimental foundation for further research and development for friction stir welding with our intellectual property rights. |
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