Microstructure and Mechanical Properties of As-cast B2-Type Zr-Co-Al AlloyPrepared by Rapid Solidification

Zr₄₉Co₄₉Al₂, Zr₄₈Co₄₈Al₄ and Zr₄₇Co₄₇Al₆ alloy bars were prepared by rapid solidification technique. The microstructure and mechanical properties of the alloys were studied. The mechanism of crack initiation and propagation in the alloys in compression was discussed. The results show that the phase of Zr₄₉Co₄₉Al₂, Zr₄₈Co₄₈Al₄ and Zr₄₇Co₄₇Al₆ alloys was B2 ZrCo phase with simple cubic structure; the (110) crystal plane spacings increased with increasing aluminum content and were all slightly larger than the theoretical value. The elastic limit and yield strength of the alloys increased with increasing aluminum content, the plastic deformation resistance decreased, the elastic energy increased, and the safety in use increased. The cracks on compression fracture surface of Zr₄₉Co₄₉Al₂ and Zr₄₈Co₄₈Al₄ alloys propagated along the stress loading direction; the grain boundary deformation and grain deformation could absorb a lot of plastic work, resulting in large plastic deformation. No crack propagation was observed on the compression fracture surface of Zr₄₇Co₄₇Al₆ alloy, and the grain boundaries and grains almost deformed at the same time, leading to the softening of the alloy at the plastic deformation stage.