In situ investigation of mechanical behavior and deformation mechanism of CoNi-based alloys
Two alloy wires,Co62Ni38 and Cr8Co62Ni30(atomic percentage),were prepared using vacuum arc melting,high-temperature forging and room temperature wire drawing techniques.Mechanical behavior of the two alloys was characterized by tensile tests,and the evolution of lattice parameters and phase structure of the alloys during deformation was explored by in situ using penetrating wide-angle X-ray diffraction technology.Subsequently,the stacking fault energy and the free energy difference between the FCC and HCP phases of the two alloys were calculated based on in-situ X-ray diffraction data,and a relationship was established with their mechanical behavior and deformation mechanism.The results show that the addition of Cr element increases the yield strength,tensile strength,uniform elongation and work hardening rate of the alloy simultaneously.The in-situ X-ray diffraction results show that no phase transformation occurs during the deformation process of the Co62Ni38 alloy,but stress-induced martensitic transformation occurs during the deformation process of the Cr8Co62Ni30 alloy.The stacking fault energy of the Cr8Co62Ni30 alloy decreases by about 18％compared to the Co62Ni38 alloy,and the free energy difference between the FCC and HCP phases decreases by about 42％.In summary,the addition of Cr element has produced a solid solution strengthening effect,effectively reducing the stacking fault energy and phase transformation free energy of the alloy,promoting stress-induced phase transformation,significantly improving the work hardening rate,and thus significantly improving the mechanical properties of the alloy.
NETL
NSTL
万方数据
