On the friction stir welding of alloy AA2014 under n-MQL cooling condition

Abstract

Friction stir welding (FSW) of AA2014 alloy requires cooling to prevent the dissolution of precipitates. The sustainable minimum quantity lubrication technique with graphene nanofluid is employed in this study for cooling purposes. FSW was carried out at 1200 rpm and 72 mm/min. A tool with a square pin was used. The microstructural evolution of the FSW joint under uniaxial tensile load is explored in detail for the first-time using electron backscatter diffraction. The results show that the grains undergo discontinuous dynamic recrystallisation during FSW and continuous dynamic recrystallisation during tensile deformation. Pole figures reveal the shear texture formed by plastic deformation. Tensile deformation has reduced local grain misorientation remarkably and thereby the dislocation accumulation. A significant increase of 94.5% is observed in grain size. Tensile deformation transforms a significant number of sub-grains with low-angle grain boundaries into stable grains with high-angle grain boundaries. The stable recrystallized grains with HAGBs and subgrains with LAGBs significantly influence the mechanical properties of the weld.

Keywords:

• Friction stir welding
• minimum quantity lubrication
• dynamic recrystallisation
• sub-grains
• local grain misorientation
• dislocation density

Disclosure statement

The authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest, or non-financial interest in the subject matter or materials discussed in this manuscript.

Data availability statement

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

Additional information

Funding

This work was supported by Anna Centenary Research Fellowship (Ref No: 19242197218/2020/AR1) provided by the Center for Research, Anna University, Chennai, Tamil Nādu, India.