Phase stabilities and equilibria of the Ti-Al-Nb ternary system at intermediate temperatures I. The 900°C isothermal section

TY - JOUR

T1 - Phase stabilities and equilibria of the Ti-Al-Nb ternary system at intermediate temperatures I. The 900°C isothermal section

AU - Xu, Shuai

AU - Lin, Junpin

AU - Liang, Yongfeng

AU - He, Jianping

AU - Chen, Xiaohua

AU - Cha, Limei

AU - Jiang, Xianquan

PY - 2022/4/15

Y1 - 2022/4/15

N2 - Determination of intermediate temperature phase diagrams is a challenging task due to sluggish transformation kinetics, metastable phases and low diffusion coefficients encountered under these conditions. The development of Ti-Al-Nb alloys has been hampered by scarcity of intermediate temperature phase diagrams. Through guidance from diffusion simulation results, we designed the composition of the diffusion components in a diffusion multiple capable of efficiently and accurately testing the Ti-Al-Nb ternary phase diagrams at intermediate temperatures, which is the service temperature of Ti-Al-Nb alloys. We systematically characterized the diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), electron backscatter diffraction (EBSD), transmission kikuchi diffraction (TKD) and transmission electron microscope (TEM), and constructed the whole composition range of the 900 °C isothermal section. The constructed range includes ten stable phases, nineteen two-phase regions and ten three-phase regions. Two ternary phases (O-Ti2AlNb and ωo-Ti4Al3Nb phases) were determined and the ωo phase was defined on the experimental phase diagram for the first time. The previous thermodynamic database at 900 °C is unreliable, based on the present work. The present experimental results will bridge the existing research gap by providing the missing thermodynamic data. The present diffusion multiple is expected to construct more isothermal sections of Ti-Al-Nb ternary system at intermediate temperatures in the future. The constructed phase diagrams are also invaluable tools to researchers and industry for development of Ti-Al-Nb alloys. © 2021 Elsevier B.V.

AB - Determination of intermediate temperature phase diagrams is a challenging task due to sluggish transformation kinetics, metastable phases and low diffusion coefficients encountered under these conditions. The development of Ti-Al-Nb alloys has been hampered by scarcity of intermediate temperature phase diagrams. Through guidance from diffusion simulation results, we designed the composition of the diffusion components in a diffusion multiple capable of efficiently and accurately testing the Ti-Al-Nb ternary phase diagrams at intermediate temperatures, which is the service temperature of Ti-Al-Nb alloys. We systematically characterized the diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), electron backscatter diffraction (EBSD), transmission kikuchi diffraction (TKD) and transmission electron microscope (TEM), and constructed the whole composition range of the 900 °C isothermal section. The constructed range includes ten stable phases, nineteen two-phase regions and ten three-phase regions. Two ternary phases (O-Ti2AlNb and ωo-Ti4Al3Nb phases) were determined and the ωo phase was defined on the experimental phase diagram for the first time. The previous thermodynamic database at 900 °C is unreliable, based on the present work. The present experimental results will bridge the existing research gap by providing the missing thermodynamic data. The present diffusion multiple is expected to construct more isothermal sections of Ti-Al-Nb ternary system at intermediate temperatures in the future. The constructed phase diagrams are also invaluable tools to researchers and industry for development of Ti-Al-Nb alloys. © 2021 Elsevier B.V.

KW - Ti-Al-Nb system

KW - TiAl based alloys

KW - Phase diagrams

KW - Diffusion multiple

KW - ωo-Ti4Al3Nb phase

U2 - 10.1016/j.jallcom.2021.163399

DO - 10.1016/j.jallcom.2021.163399

M3 - 文章

SN - 0925-8388

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

ER -