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

Mohammadi, J ; Sharif University of Technology | 2015

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  1. Type of Document: Article
  2. DOI: 10.1016/j.matchar.2015.01.008
  3. Publisher: Elsevier Inc , 2015
  4. Abstract:
  5. 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 Al12Mg17 (γ) and Al3Mg2 (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 Al12Mg17 (γ) and Al3Mg2 (β)
  6. Keywords:
  7. Dissimilar materials joining ; Alloys ; Aluminum ; Aluminum alloys ; Brittle fracture ; Characterization ; Dissimilar materials ; Electron probe microanalysis ; Energy dispersive spectroscopy ; Fracture ; Friction ; Intermetallics ; Joining ; Magnesium ; Magnesium alloys ; Mechanical properties ; Microstructure ; Research laboratories ; Rotation ; Scanning electron microscopy ; Soldered joints ; Speed ; Stainless steel ; Strain ; Stress-strain curves ; Stresses ; Tensile strength ; Tensile testing ; Tribology ; Welding ; Welds ; X ray diffraction ; X ray spectroscopy ; 6061 aluminum alloys ; AZ31B magnesium alloys ; Energy dispersive X ray spectroscopy ; Friction stir welding joints ; Joint tensile strengths ; Mechanical characterizations ; Microhardness measurement ; Microstructure characterization ; Friction stir welding
  8. Source: Materials Characterization ; Volume 101 , March , 2015 , Pages 189-207 ; 10445803 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S1044580315000108