Shang Guoqiang, Gan Xueping, Wang Xinnan, Ge Jinyang, Li Chao, Zhu Zhishou, Zhang Xiaoyong, Zhou Kechao
State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China.
Key Laboratory of Advanced Titanium Alloys, AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China.
Materials (Basel). 2024 Oct 13;17(20):5010. doi: 10.3390/ma17205010.
The α variant selection and microstructure evolution in a new metastable β titanium alloy TB17 were studied in depth by DTA, microhardness, XRD, SEM, and EBSD characterization methods. Under the rapid cooling rate conditions (150 °C/min-400 °C/min), only a very small amount of granular α (α Widmanstatten precipitates within the grains) precipitated within the grains. The secondary α phase precipitated in the alloy changed from granular to fine needle-like at moderate cooling rates (15 °C/min-20 °C/min). When continuing to slow down the cooling rates (10 °C/min and 1 °C/min), the α (α precipitates along the β grain boundaries), α (α Widmanstatten precipitates that developed from β grain boundaries or α) and α grew rapidly. Moreover, the continuous cooling transformation (CCT) diagram illustrated the effect of cooling rate on the β/α phase transition. EBSD analysis revealed that the variants selection of α near the original β grain boundary is mainly divided into three categories. (i) The double-BOR (Burgers orientation relationship) α colonies within neighboring β grains grow in different directions but have the same crystallographic orientation. (ii) The double-BOR α colonies within neighboring β grains have different growth directions and different crystallographic orientations. (iii) The double-BOR α colonies within the same grain have the same growth direction, but different crystallographic directions. And these double-BOR α colonies correspond to two variants of the given {0001}α//{110}β.
通过差示扫描量热法（DTA）、显微硬度测试、X射线衍射（XRD）、扫描电子显微镜（SEM）和电子背散射衍射（EBSD）表征方法，对新型亚稳β型钛合金TB17中的α变体选择和微观结构演变进行了深入研究。在快速冷却速率条件（150℃/min - 400℃/min）下，晶粒内部仅析出极少量的粒状α（α魏氏组织在晶粒内部析出）。在中等冷却速率（15℃/min - 20℃/min）下，合金中析出的次生α相从粒状变为细针状。当继续降低冷却速率（10℃/min和1℃/min）时，α（α沿β晶界析出）、α（从β晶界或α发展而来的α魏氏组织）迅速长大。此外，连续冷却转变（CCT）图展示了冷却速率对β/α相变的影响。EBSD分析表明，原始β晶界附近α的变体选择主要分为三类。（i）相邻β晶粒内的双BOR（伯格取向关系）α晶团生长方向不同，但晶体学取向相同。（ii）相邻β晶粒内的双BOR α晶团生长方向不同，晶体学取向也不同。（iii）同一晶粒内的双BOR α晶团生长方向相同，但晶体学方向不同。并且这些双BOR α晶团对应于给定的{0001}α//{110}β的两个变体。
