Erik Kostson
Ansys Employee

SOLID5 is an old legacy element, that is not recommended anymore (also it is a 8 node hex or 6 node prism).

The recommended element to use for coupled analysis (e.g., thermal-struct.) is the solid226 with keyopt(1)=11 for thermal structural analysis (it is a 20 node hex element, ...) .
They (226) are also used inside Workbench and in the coupled static system which is for thermal structural analysis and is the recommended way to perform this.

All the best