Yu-peng ZHANG, Zhong-feng CHEN, De-bin ZHENG, Cui-ping WANG, Hao-jun ZHUO, Xiang YU, Yue-chao CHEN, Shui-yuan YANG, Yi-lu ZHAO, Xing-jun LIU
Low-density superalloys
often exhibit low yield strength in the intermediate temperature range
(300−650 °C). To enhance yield performance in this range, the CALPHAD
method was used to design a new Co-based superalloy. The
Co−30Ni−10Al−3V−6Ti−2Ta alloy, designed based on γʹ phase dissolution
temperature and phase fraction, was synthesized via arc melting and heat
treatment. Phase transition temperatures, microstructure evolution, and
high-temperature mechanical properties were characterized by differential scanning
calorimetry, scanning electron microscopy, dual-beam TEM, and compression
tests. Results show that the alloy has low density (8.15 g/cm³) and high γʹ dissolution temperature (1234 °C), along with unique yield strength retention
from room temperature to 650 °C. The yield strength anomaly (YSA) is
attributed to high stacking fault energy and activation of the Kear−Wilsdorf
locking mechanism, contributing to superior high-temperature stability of the
alloy. The yield strength of this alloy outperforms other low-density Co-based
superalloys in the temperature range of 23−650 °C.
