Indentation hardness

Engineering

Metallurgy

Materials science

Intermetallic

Friction stir welding

Ultimate tensile strength

Joint (building)

Indentation

Thermodynamics

Physics

Diffusion

Alloy

Microstructure

Optical microscope

Composite material

Structural engineering

Scanning electron microscope

Friction welding

Welding

Materials Science and Engineering A

Conventional and cooling assisted friction stir welded Al–Mg joints were investigated by visual inspection, optical macro plus microscopy, scanning electron micrographs, energy dispersive X-ray spectroscopy, X-ray diffractions, tensile testing and micro hardness indentation. The nugget zone is characterized by onion rings composed of different phases such as Mg in an Al matrix, Al in an Mg matrix as well as intermetallic compounds, Al3Mg2 and Al12Mg17. A diffusion layer was detected on the Al side of the joint between the nugget and thermo-mechanically affected zones identifying a solid solution of Mg in Al. No diffusion layer was observed on the Mg side. The tensile strength of the dissimilar joints is enhanced by cooling assisted welding process due to the reduction in the amount of intermetallic compounds inside the weld bead. Congruently, higher hardness peaks are reported in the nugget zone of conventional FSW joint with respect to the CFSW joint.

Conventional and cooling assisted friction stir welding of AA6061 and AZ31B alloys