Friction stir welding joint of dissimilar materials between AZ31B magnesium and 6061 aluminum alloys: Microstructure studies and mechanical characterizations

Journal Article · Sun Mar 15 00:00:00 EDT 2015 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2015.01.008· OSTI ID:22476064

Mohammadi, J. ^[1]; Behnamian, Y. ^[2]; Izadi, H. ^[2]; Saeid, T. ^[3]; Kokabi, A. H. ^[4]

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1. Department of Materials Science and Engineering, Science and Research Branch, Islamic Azad University, Tehran 141554933 (Iran, Islamic Republic of)
2. Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada)
3. Faculty of Materials Engineering, Sahand University of Technology, Tabriz 513351996 (Iran, Islamic Republic of)
4. Department of Materials Science and Engineering, Sharif University of Technology, Tehran 113659466 (Iran, Islamic Republic of)

Friction stir welding is an efficient manufacturing method for joining dissimilar alloys, which can dramatically reduce grain sizes and offer high mechanical joint efficiency. Lap FSW joints between dissimilar AZ31B and Al 6061 alloy sheets were made at various tool rotation and travel speeds. Rotation and travel speeds varied between 560–1400 r/min and 16–40 mm/min respectively, where the ratio between these parameters was such that nearly constant pitch distances were applied during welding. X-ray diffraction pattern (XRD), optical microscopy images (OM), electron probe microanalysis (EPMA) and scanning electron microscopy equipped with an energy-dispersive X-ray spectroscopy (SEM-EDS) were used to investigate the microstructures of the joints welded. Intermetallic phases including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β) were detected in the weld zone (WZ). For different tool rotation speeds, the morphology of the microstructure in the stir zone changed significantly with travel speed. Lap shear tensile test results indicated that by simultaneously increasing the tool rotation and travel speeds to 1400 r/min and 40 mm/min, the joint tensile strength and ductility reached a maximum. Microhardness measurements and tensile stress–strain curves indicated that mechanical properties were affected by FSW parameters and mainly depended on the formation of intermetallic compounds in the weld zone. In addition, a debonding failure mode in the Al/Mg dissimilar weld nugget was investigated by SEM and surface fracture studies indicated that the presence of intermetallic compounds in the weld zone controlled the failure mode. XRD analysis of the fracture surface indicated the presence of brittle intermetallic compounds including Al{sub 12}Mg{sub 17} (γ) and Al{sub 3}Mg{sub 2} (β). - Highlights: • Dissimilar Al/Mg joint was obtained by lap friction stir welding technique. • Effect of rotation and travel speeds on the formation of intermetallic compounds • Microstructure and chemical studies including metallography, XRD, SEM-EDS, and EPMA • Mechanical property tests such as stress–strain curves, failure load and hardness • IMCs as Al{sub 3}Mg{sub 2} and Al{sub 12}Mg{sub 17} were identified in weld nugget and at Al/Mg interface.

• OSTI ID: 22476064
• Journal Information: Materials Characterization, Vol. 101; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
DUCTILITY
ELECTRON MICROPROBE ANALYSIS
FRICTION
GRAIN SIZE
INTERFACES
INTERMETALLIC COMPOUNDS
MAGNESIUM ALLOYS
METALLOGRAPHY
MICROHARDNESS
OPTICAL MICROSCOPY
ROTATION
SCANNING ELECTRON MICROSCOPY
STRAINS
STRESSES
SURFACES
WELDED JOINTS
WELDING
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY