Microstructure and mechanical properties of novel B2-type ductile Zr-Co-Cu alloys containing the B33 phase

Microstructure and mechanical properties of novel B2-type ductile Zr-Co-Cu alloys that contain the B33 phase were investigated. The normalized value of the diffraction intensity of the B33 phase increases with an increase in the Cu content, and the volume fractions of the B33 phase correspondingly increase. The parent phases of the Zr-Co-Cu alloys are composed of B2 phases; in addition, the B33 phase forms along the crystal boundary. The addition of small amounts of the element Cu improves the yield strength, the elastic limit, and Young's modulus of the alloys; it also maintains the ductility of the Zr-Co-Cu alloys. The Zr47Co47Cu6 alloy that has a lower work-hardening index has a high yield strength of 640 MPa, an elastic limit of 458 MPa, and good ductility. These are attributed to the increasing volume fraction of the B33 phases and to the grain refining of the B2 parent phases.