Phase transformation behavior and kinetics of high Nb–TiAl alloy during continuous cooling
Phase transformation behavior and kinetics of high Nb–TiAl alloy during continuous cooling
复制标题
DOI：
10.1016/j.jallcom.2016.01.205
复制
发表时间：
2016-05
影响因子：
6.2
通讯作者：
Ying Li;Lian Zhou;Junpin Lin;Hui Chang;Lina Feng
中科院分区：
文献类型：
--
作者：
Ying Li;Lian Zhou;Junpin Lin;Hui Chang;Lina Feng
Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y（at.研究了3 °C/min、5 °C/min、10 °C/min、20 °C/min、40 °C/min冷却速率下连续冷却和水淬（WQ）过程中合金的凝固行为。利用X射线衍射仪（XRD）和光学显微镜（OM）分别对合金的相组成和显微组织进行了研究。采用硬度计（DIL）研究了合金在连续冷却过程中的膨胀和相体积分数的变化，并采用显微硬度计测试了合金在冷却过程中的显微硬度。结果表明，在连续冷却过程中，合金发生了由母相α向γ和α 2的相变，α→γ相变发生在1150 °C ~ 1310 °C之间，α→α 2相变发生在1100 °C ~ 1220 °C之间。相变温度随冷却速率的增大而降低，冷却速率越大，相变速率越大。冷却速率对γ相和α 2相的相对含量有很大的影响，随冷却速率的增加，晶体组织的片层团尺寸和片层间距减小。高Nb-TiAl合金的显微硬度随着冷却速度的增加而增加，这是由于相组成和晶体结构的变化所致。
Phase transformation behavior and kinetics of Ti–45Al–8.5Nb–0.2W–0.2B–0.02Y (at. %) alloy during continuous cooling under the cooling rates of 3 °C/min, 5 °C/min, 10 °C/min, 20 °C/min, 40 °C/min and water quenching (WQ) were investigated in this study. The phase composition and microstructure of the alloy were studied using X-ray diffraction (XRD) and optical microscopy (OM), respectively. The expansion and the volume fraction evolution of phases during continuous cooling were investigated by dilatometry (DIL), and the microhardness of the alloy suffered from cooling was also tested through micro-sclerometer. The results indicate that the phase transformation from parent α phase to γ and α2take place during continuous cooling, the α→γ phase transformation occurs in the temperature range of 1150 °C–1310 °C while the α→α2phase transformation takes place between 1100 °C and 1220 °C. The transformation temperature decreases with the cooling rate increasing, and the higher the cooling rate is, the higher the phase transformation rate is. The relative fraction of γ phase and α2phase much depend on the cooling rate, and the lamellar colony sizes and interlamellar spacing of crystal structure decrease with the cooling rate increasing. The microhardness of high Nb–TiAl alloy increases with the cooling rate increasing due to the variations of phase composition and crystal structure.