Improvements in friction stir welding strength considering design and process parameters by using Aluminum alloy AA7075-T6

Abstract In this research work tool rotational speed, tool hardness, shoulder to pin diameter ratio and welding speed/ feed were selected as the parameters to see how we can increase the quality of the weld by varying these parameters. Highlights of this research work are: (a) Efficient tool design regarding material selection for the tool and design of the tool (D/d ratio) (b) Effects of FSW parameters mostly tool rotational speed on mechanical properties related to quality and strength of the weld (c) effect of tool hardness and welding speed on strength of friction stir welding. Design of experiment software was used to design experiments and tool geometry. Another technique that was used in this research was related to regression analysis to forecast the tensile strength and hardness of friction stir welded joint. The Tensile strength and hardness were the output responses. From the investigation of influence of the parameters it was concluded that welding speed is the most significant parameter while rotational speed, Tool hardness and D/d ratio are least significant parameters however these parameters still affect the quality of weld. An evaluation was made between measured and predicted results by developing a regression model and the values obtained for the response tensile strengths and hardness were compared with measured values. SEM analysis was done on the low medium and high values samples to visualize the grain structure by fractography. Three confirmation tests were carried out in order to validate the regression models.