The barrier-free nanomultilayered structure via enthalpy-mediated phase separation in refractory high-entropy films

Patterned metal systems to periodically modulated nanomultilayered architectures, with crystalline and/or amorphous states, has acted as an effective strategy for tuning desirable mechanical properties. While the spontaneous assembly offers an effective and promising path for constructing nanomultilayers, in high-entropy alloys (HEA) how to trigger such a barrier-free route still faces challenges. In this paper, the enthalpy-differenceguided strategy, incorporating Pt, was employed to induce spinodal decomposition for the barrier-free nanomultilayer structure in refractory HEA systems. Aiming at exploring the elastic and chemical interactions, three HEA films with different degrees of size mismatch delta (Zr-Nb-Ta-Mo-W, Zr-Hf-Nb-Ta-Mo, Zr-Hf-Nb-Cr-Mo systems) were fabricated as model systems. Contributed by differences in Delta Hmix and delta, in each HEA film, certain-content Pt can trigger both spinodal decomposition and amorphization behavior, which lead to the barrier-free Pt-rich/Ptlean nanomultilayers with different topological combinations: crystalline/crystalline and amorphous/amorphous. Compared to model HEAs, such barrier-free nanomultilayers can significantly improve the nanoindentation hardness. In HEA systems, tuning Delta Hmix and delta simultaneously can assist the further understanding of the structural arrangements and the progress on the barrier-free nanomultilayered configuration for superior mechanical properties.