1 School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China 2 Materials Genome Institute, Shanghai University, Shanghai 200444, China 3 State Key Laboratory of Advanced Special Steel, Shanghai University, Shanghai 200444, China 4 School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, Guangxi, China
Experimental study of phase equilibria on Co–Fe-rich side of Co–Al–Fe system
1 School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China 2 Materials Genome Institute, Shanghai University, Shanghai 200444, China 3 State Key Laboratory of Advanced Special Steel, Shanghai University, Shanghai 200444, China 4 School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, Guangxi, China
摘要 Despite various studies on Co–Al–Fe ternary system, its phase equilibria are still in doubt. Phase equilibria, magnetic transition and bcc_A2/bcc_B2 order–disorder transformation at the Co–Fe-rich side of the Co–Al–Fe alloys were carefully investigated by means of electron probe microanalysis (EPMA), X-ray diffraction (XRD) and differential scanning calorimetry. The equilibrium phases and their compositions were determined by 18 alloy samples annealed at 900, 1000, 1100 and 1200 °C for 528, 336, 168 and 96 h, respectively, followed by quenching. However, by adopting the above traditional method, bcc_A2 and fcc_A1 phases are difficult to be distinguished through XRD analysis at room temperature due to the martensitic transformation of fcc_A1 phase during quenching. For this reason, high-temperature in situ XRD technique was utilized to correctly establish the phase relationships among bcc_A2, bcc_B2 and fcc_A1 phases. The phase transformation between bcc_A2 and B2 phases was determined to be second order instead of first order at temperatures higher than 900 °C. The equilibrium phases and compositions were further confirmed by fabricating 16 diffusion couples together with EPMA. Meanwhile, using three-dimensional differential scanning calorimetry method, bcc_A2/B2 and ferro-/paramagnetic transitions were determined with high accuracy.
Abstract：Despite various studies on Co–Al–Fe ternary system, its phase equilibria are still in doubt. Phase equilibria, magnetic transition and bcc_A2/bcc_B2 order–disorder transformation at the Co–Fe-rich side of the Co–Al–Fe alloys were carefully investigated by means of electron probe microanalysis (EPMA), X-ray diffraction (XRD) and differential scanning calorimetry. The equilibrium phases and their compositions were determined by 18 alloy samples annealed at 900, 1000, 1100 and 1200 °C for 528, 336, 168 and 96 h, respectively, followed by quenching. However, by adopting the above traditional method, bcc_A2 and fcc_A1 phases are difficult to be distinguished through XRD analysis at room temperature due to the martensitic transformation of fcc_A1 phase during quenching. For this reason, high-temperature in situ XRD technique was utilized to correctly establish the phase relationships among bcc_A2, bcc_B2 and fcc_A1 phases. The phase transformation between bcc_A2 and B2 phases was determined to be second order instead of first order at temperatures higher than 900 °C. The equilibrium phases and compositions were further confirmed by fabricating 16 diffusion couples together with EPMA. Meanwhile, using three-dimensional differential scanning calorimetry method, bcc_A2/B2 and ferro-/paramagnetic transitions were determined with high accuracy.
Jing‑jing Wang,Wei‑sen Zheng,Xiao‑gang Lu, et al. Experimental study of phase equilibria on Co–Fe-rich side of Co–Al–Fe system[J]. Journal of Iron and Steel Research International, 2020, 27(6): 673-680.
2020, Vol. 27 
