RF hardware is unforgiving: a waveguide that is not to size loses signal, and a mount that moves with temperature takes the antenna off point. Precision is not a nice-to-have here.
Waveguide sections and flanges, housings and enclosures, structural brackets and mounts, and filter bodies.
Aluminum for low weight, titanium where strength-to-weight and temperature matter, Kovar and Invar where dimensional stability or a glass/ceramic joint is required.