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Abstract
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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.
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