The Cu‐Cr system exhibits a miscibility gap in the liquid and has essentially no solid solubility. However, using low energy, <160 eV, Ar+ ion bombardment of the growing film to promote ballistic collisional mixing, metastable single phase face‐centered‐cubic Cu‐rich and body‐centered‐cubic Cr‐rich solid solutions have been grown on amorphous glass substrates at 75 °C. The films were typically 1 μm thick with average grain sizes of 90 and 110 nm, respectively, and a (111) preferred orientation. Annealing studies combined with x‐ray and electron diffraction analyses showed that the films have good thermal stability against phase separation at temperatures up to 400 °C. The metastable to equilibrium phase transformation occurred with the precipitation of an essentially pure second phase, rather than through a continuous series of metastable states, due to structural constraints.