In-situ TEM-heating study of the microstructural evolution of CrFeCoNiCu high entropy
alloy (HEA) thin films was carried out and morphological and phase changes were recorded.
Post annealing investigation of the samples was carried out by high resolution electron
microscopy and EDS measurements. The film is structurally and morphologically stable
single phase FCC HEA up to 400 °C. At 450 °C the formation of a BCC phase was observed,
however, the morphology of the film remained unchanged. This type of transformation
is attributed to diffusionless processes (martensitic or massive). From 550 °C fast
morphological and structural changes occur, controlled by volume diffusion processes.
Fast growing of a new intermetallic phase is observed which contains mainly Cr and
has large unit cell due to chemical ordering of components in <100> direction. The
surface of the films gets covered with a CrO-type layer, possibly contributing to
corrosion resistance of these.
