Welding processes are extensively used to assemble components in many manufacturing industries, such as aeronautics, construction, energy and automotive. To increase their productivity, constructors try to reduce manufacturing time. This involves for welding operations an increase of welding speed. However, various defects such as hot tearing might limit this increase. Hot tearing appears at the solidification end of an alloy, and is commonly observed in welding. During welding, components are subjected to high thermal gradients around the melting zone due to localized heat input. The solidification zone, where microstructure forms, is located at the rear of the melting zone and is bordered by two isothermal surfaces corresponding to liquidus and solidus temperatures. In welding, due to high thermal gradients, solidification by epitaxial growth of columnar dendrites is generally observed from the border of the melting zone. However, equiaxed dendritic grains can also form in the center area of the melting zone.