Abstract
Metallic alloys with high strength and large ductility are required for extreme structural applications.However,the achievement of ultrahigh strength often results in a substantially decreased ductility.Here,we report a strat-egy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1 2-strengthened superlattice alloy.As a proof of con-cept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi2(Al0.2Nb0 2)alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni3(Al,Nb)-type ordered nanoprecipitates(～12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33％.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity.This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.
基金项目
Microscope and Imaging Center at Southern University of Science and Technology,China()
国家自然科学基金(52122102)
Guangdong Innovative & Entrepreneurial Research Team Program(2016ZT06C279)
Inter-University 3D APT Unit of City University of Hong Kong(CityU)()
CityU grant(9360161)
NETL
NSTL
万方数据