Novel class of amorphous/crystalline high entropy alloys multilayer thin films with superior mechanical properties and thermal stability
Résumé
The design of high performance structural materials is always pursuing combinations of excellent yet often mutually exclusive mechanical properties and thermal stability. Although crystal-glass composite alloys provide better ductility compared to fully amorphous alloys, their thermal stability is poor, due to heterogeneous nucleation at the crystal-glass interface [1, 2].
Here, we present a new strategy to develop thermally stable, ultrastrong and deformable crystal-glass nanocomposites through a thermodynamically guided alloy design approach, which mimics the mutual stabilization principle known from symbiotic ecosystems. We realized this in form of a model Cr-Co-Ni (crystalline)/Ti-Zr-Nb-Hf-Cr-Co-Ni (amorphous) laminate composite alloy (see Figure) [3].
The symbiotic alloy has an ultrahigh compressive yield strength of 3.6 GPa and large homogeneous deformation of ~15% strain at ambient temperature, values which surpass those of conventional metallic glasses and nanolaminate alloys (see Figure). Furthermore, the alloy exhibits ~200 K higher crystallization temperature (TX> 973 K) compared to that of the original TiZrNbHf-based amorphous phase. The elemental partitioning among adjacent amorphous and crystalline phases leads to their mutual thermodynamic and mechanical stabilization, opening up a new symbiotic approach for stable, strong and ductile materials [3].
References:
[1] W. Guo et al., Acta Mater. 80 (2014) 94-106.
[2] D.B. Miracle, O.N. Senkov, Acta Mater. 122 (2017) 448-511.
[3] M. Ghidelli et al., Submitted to Materials Today (2021)