Remarkable Damage Tolerance of the Medium-Entropy Alloy CrCoNi
In the range 77-293K, the alloy shows a combination of strength and fracture toughness up to 1.3 GPa and ~275 MPa.m1/2, respectively, which together with the increasing fracture resistance (J-integral) with crack extension makes this medium-entropy alloy an exceptionally damage tolerant material.
Based on the design concept of high-entropy alloys (HEAs), this medium-entropy alloy CrCoNi yields a material with damage-tolerance that surpasses literally all HEAs and most conventional alloys to date.
Significance and Impact
The material shows increasing strength, ductility and toughness with decreasing temperature, which is contrary to the behavior of most conventional alloys that generally show embrittlement.
- The medium-entropy alloy CrCoNi is an equiatomic, single-phase material with fully recrystallized, equiaxed grains of 5-50 µm size.
- From room to liquid nitrogen temperature, the fracture toughness increases from ~210 to ~275 MPa.m1/2 through pronounced dislocation activity in form of cell structure formation and excessive nano-scale deformation twinning. Such mechanisms lead to excessive strain hardening with increasing strength and ductility at decreasing temperatures.