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Intermetallic Compounds in the Banded Structure and Their Effect on Mechanical Properties of Al/Mg dissimilar friction stir welding Joints

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Journal of Materials Science & Technology 2017年第4期33卷 359-366页

作者： Hui Shi Ke Chen Zhiyuan Liang Fengbo Dong Taiwu Yu Xianping Dong Lanting Zhang Aidang Shan Shanghai Key Lab of Advanced High-Temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Department of Mechanical Engineering University of Hong KongPokfulam RoadHong KongChina Special welding Technology Center Shanghai Aerospace Equipments ManufacturerShanghai 200245China

dissimilar friction stir welding（FSW） between aluminum and magnesium alloy was performed, using various tool rotational speed（TRS） at a ？xed travel speed, with tool offset to aluminum to investigate the formation of intermetallic compounds（IMCs） in the banded structure（BS） zone and their effect on mechanical properties. Large quantities of IMCs, in the form of alternating bands of particles or lamellae, were found in the BS zone, where drastic material intermixing occurred during FSW. The BS microstructural characters in terms of the morphology of the bands and the quantity and distribution of IMC particles varied with TRS. All welds exhibited brittle fracture mode with their fracture paths propagating mainly in/along the IMCs in the BS. It is shown that these BS microstructural characters have significant effect on the mechanical properties of the joints. Suggestions on tailoring the BS microstructure were proposed for improving the strength of the BS zone and the final mechanical properties of the Al/Mg FSW joints.

关键词： Banded structure Intermetallic compounds dissimilar friction stir welding Mechanical properties

Influence of tool pin design on properties of dissimilar copper to aluminum friction stir welding

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Transactions of Nonferrous Metals Society of China 2017年第1期27卷 36-54页

作者： Kush P.MEHTA Vishvesh J.BADHEKA Department of Mechanical Engineering School of TechnologyPandit Deendayal Petroleum UniversityRaisanGandhinagar 382007India

dissimilar friction stir welding （FSW） of copper and aluminum was investigated by nine different tool designs, while the rest of the process parameters were kept constant. Mechanical and metallurgical tests such as macrostructure, microstructure, tensile test, hardness, scanning electron microscope and electron X-ray spectrographs were performed to assess the properties of dissimilar joints. The results exhibited that, the maximum joint strength was achieved by the tool of cylindrical pin profile having 8 mm pin diameter. Besides, the fragmental defects increased as the number of polygonal edges decreased, hence the polygonal pin profiles were unsuitable for dissimilar FSW butt joints. Furthermore, the tensile strength increased as the number of polygonal edges increased. stir zone of polygonal pin profiles was hard and brittle relative to cylindrical tool pin profiles for same shoulder surface. Maximum hardness of HV 283 was obtained at weld made by the polygonal square pin profile. The hard and brittle intermetallic compounds （IMCs） were prominently presented in the stir zone. Phases of IMCs such as CuAl, CuAl2, Cu3Al and Cu9Al4 were presented in the stir zone of dissimilar Cu-Al joints.

关键词： Cu-Al joint dissimilar friction stir welding pin profiles properties intermetallic

Effect of reverse dual rotation process on properties of friction stir welding of AA7075 to AISI304

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Transactions of Nonferrous Metals Society of China 2019年第5期29卷 964-975页

作者： Hamed JAMSHIDI AVAL Altino LOUREIRO Department of Materials Engineering Babol Noshirvani University of TechnologyShariati AvenueBabolIran CEMUC Department of Mechanical EngineeringUniversity of CoimbraRua Luís Reis Santos3030-788 CoimbraPortugal

The friction stir lap welding of AISI304 stainless steel to AA7075 aluminium alloy was investigated using the conventional friction stir welding (C-FSW) and the reverse dual rotation friction stir welding (DR-FSW) processes. In order to reduce the heat input, a dual rotation tool with a lower shoulder rotating speed was used. The results showed that both processes provide welds with excellent appearance and free of internal defects. The use of the DR-FSW process with the tool shoulder rotating reversely at low speed results in larger grain refinement in the nugget and less change in the microstructure of the aluminium alloy than using the C-FSW. The use of DR-FSW process at low speed of rotation allows to reduce the amount of intermetallic compounds in the welding interface, but does not prevent their formation. Although DR-FSW welding exhibits tensile strength superior to that achieved with the conventional process (C-FSW), both exhibit brittle behaviour with fracture at the weld interface.

关键词： dual rotation tool dissimilar friction stir welding AA7075 AISI304 microstructure mechanical properties