Influence of solute partitioning on the microstructure and growth stresses in nanocrystalline Fe(Cr) thin films

This paper addresses how solute segregation and phase separation evolves the intrinsic growth stresses for Fe-4Cr and Fe-16Cr (at.%) nanocrystalline films. Ambient temperature deposition resulted in both alloys exhibiting a near equivalent tensile stress though the average grain sizes were approximately 50 nm and 100 nm respectively. Upon heating during deposition to 523 K and 673 K, the tensile stress was reduced in each film and it eventually became compressive for the higher deposition temperature. Interestingly, the Fe-16Cr film, at the higher heating temperature, diverted from the steady state compressive stress towards a tensile stress after approximately 150 nm of growth. The collective stress evolution of these films is discussed in terms of their phase separation, which can include spinodal deposition, as a function of Cr content and processing temperature. It was found that Cr acted as a grain refiner which appeared to dominate the film microstructure and associated stress response.