For the thermal analysis, the initial temperature of each part must be specified. The interface between the moving weld pool and its complement is a Dirichlet BC on the complement. The value of Dirichlet BC is the specific enthalpy of solid at the solidus temperature. There is also a weld velocity that is ‘parallel’ or tangential to the weld joint ‘ribbon’.

The thermal solution drives the microstructure evolution and the thermal stress solver. The thermal properties required to solve the thermal problem are:

- specific enthalpy as a function of temperature and microstructure

- specific heat preferably as a function of specific enthalpy but often provided as a function of temperature and microstructure

- thermal conductivity as a function of temperature and microstructure

- latent heats of phase transformation; Each phase transformation can have an associated latent heat