Abstract

Medium-entropy alloy (MEA) CrCoNi with gradient microstructure was processed by severe torsion deformation at the torsional speed of 0.5π radian/s. Different gradient microstructures were obtained by choosing different torsional angles. Uniaxial tensile tests show that the strength increases and the uniform elongation decreases with the increasing torsional angle. In particular, MEA processed by torsion at the torsional angle of 20π possesses high strength without comprising the ductility. Compared with the initial sample, the yield strength in the gradient nanotwinned MEA is increased from 245 MPa to 760 MPa while ~31% uniform elongation is maintained. Microstructural observations show that gradient dislocation density and gradient nanotwins contribute to the superior mechanical properties. A theoretical model considering the gradient dislocation density and the gradient nanotwins was proposed to explore the effect of gradient microstructure on the mechanical properties. The theoretical analyses reveal that the enhanced strength is attributed to the forest dislocations and nanotwins. The gradients of dislocation and nanotwins provide extra strain hardening capability for improving the ductility.

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call