Effect of tool pin-tip profiles on material flow and mechanical properties of friction stir welding thick AA7075-T6 alloy joints

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• 作者：Mao Yuqing ; Ke Liming ; Liu Fencheng…
• 关键词：Friction stir welding ; Pin ; tip profile ; Thermal cycles ; Material flow ; EBSD ; Mechanical properties
• 刊名：The International Journal of Advanced Manufacturing Technology
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：88
• 期：1-4
• 页码：949-960
• 全文大小：
• 刊物类别：Engineering
• 刊物主题：Industrial and Production Engineering; Media Management; Mechanical Engineering; Computer-Aided Engineering (CAD, CAE) and Design;
• 出版者：Springer London
• ISSN：1433-3015
• 卷排序：88

文摘

Five tools with different pin-tip profiles like thread taper, triangular, square, three grooves, and conical platform were designed to friction stir weld 20-mm-thick AA7075 alloy plates. The effects of pin-tip profiles on thermal cycles, material flow, and mechanical properties of the joints were studied. The results show that the temperature greatly decreases from the top to the bottom of the weld, and higher peak temperatures along the thickness are obtained using three grooves tool. Due to poor plastic flow reflected by local transfer behavior of material, thread taper and conical platform tools yield macro cross-sectional level pore defect on advancing side in nugget zone. However, triangular, square, and three grooves tools produce defect-free joints due to improving plastic flow resulted from stronger pulsating action and stirring power, leading to higher transfer displacements of local material. The tensile test results show that the joints fabricated by three grooves tool have better mechanical properties including strength and ductility owing to better material flow. A higher ultimate tensile strength of 391 ± 10 MPa, yield strength of 310 ± 12 MPa, and elongation of 8.3 % are obtained, respectively. This can be attributed to finer grains, greater natural aging response and optimum hardness.