Suppressing temperature-dependent embrittlement in high-strength medium-entropy alloy via hetero-grain/precipitation engineering

Hetero-grain/precipitation engineering was adopted to improve mechanical properties of alloy over a wide temperature range. Partial recrystallization and L12 nanoprecipitation were simultaneously introduced into a CoCrNi-based medium entropy alloy, resulting in a heterogeneous microstructure. This kind of heterostructured alloy achieves an ultrahigh tensile strength of 1.5 GPa at 500 degrees C, and still maintains a tensile strength above 1.1 GPa at 600 degrees C. All elongations exceed 20% at-196 degrees C and elevated temperatures up to 700 degrees C, which indicates the breakthrough in temperature-dependent embrittlement encountered by many structural materials with equiaxed grain structures. Such a superior combination of strength and ductility at elevated temperatures can be ascribed to the stable deformed grains and pronounced planar defects, including stacking fault networks and deformation twins. This work demonstrates that hetero-grain/precipitation engineering can provide an effective strategy to achieve high strengths of alloys without sacrificing ductility over an extended temperature range.

Automated summary

Hetero-grain/precipitation engineering was used to improve the mechanical properties of an alloy over a wide temperature range. By introducing partial recrystallization and L12 nanoprecipitation, a heterogeneous microstructure was achieved in a CoCrNi-based medium entropy alloy. This alloy demonstrated an ultrahigh tensile strength of 1.5 GPa at 500 degrees C and maintained a tensile strength above 1.1 GPa at 600 degrees C. Furthermore, it exhibited excellent elongation properties at temperatures ranging from -196 degrees C to 700 degrees C, overcoming temperature-dependent embrittlement commonly observed in materials with equiaxed grain structures. The superior combination of strength and ductility at elevated temperatures was attributed to the stable deformed grains and pronounced planar defects present in the alloy.