High-resolution EBSD characterisation of friction stir welded nickel–copper alloy: effect of the initial microstructure on microstructural evolution and mechanical properties

ABSTRACT

The effect of the initial structure on the microstructure and texture of the friction stir welded Monel 400 alloy joints was investigated. For this aim, Monel 400 alloy of two initially treated conditions, annealed and rolled, was studied. Orientation imaging microscopy with a step size of 70 nm was used to characterise the microstructures of the joints. The mechanical properties were evaluated using Vickers hardness and nanoindentation tests. In the joint of the initial annealed alloy, continuous dynamic recrystallisation governed the grain structure formation. However, in the case of the initial rolled base material, discontinuous dynamic recrystallisation also occurred to cause more random texture, smaller grains, much more high-angle grain boundaries and higher dislocation densities. In the stir zone, the hardness and yielding strength increased respectively from 177 HV to 192 HV and 215.9 to 238.8 MPa by changing the base metal from the initial annealed to rolled condition. In addition, the microstructural features of the different zones containing the texture components and grain boundaries were scrutinised thoroughly.

KEYWORDS:

• Texture
• microstructure
• EBSD
• recrystallisation
• nanoindentation

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Yutao Pei http://orcid.org/0000-0002-1817-2228