摘要
采用预合金粉末热等静压工艺制备了名义成分为Ti-22Al-24.5Nb-0.5Mo (原子分数,%)的Ti-2AlNb合金及大尺寸异形环坯(直径大于800 mm),采用热模拟压缩实验研究了Ti-2AlNb粉末合金的热变形行为,并对异形粉末环坯进行了轧制实验,分析了轧制前后的组织性能变化。结果表明,Ti-2AlNb粉末合金的热加工窗口宽且开裂倾向小,具有更均匀的化学成分和α2相分布,但其应力抖动更加明显。优选1035~1045℃为Ti-2AlNb粉末异形环的变形温度区间,Ti2AlNb粉末异形环坯经两火轧制后,无损检测表明无任何裂纹产生。热变形促使Ti-2AlNb粉末合金的O板条细化和α2相球化,热处理后,粉末制坯+环轧成形Ti-2AlNb合金为近两相(B2+O)组织,合金的室、高温拉伸塑性显著提高。
Ti2AlNb alloy was considered as the candidate material to replace superalloys such as GH4169 in gas turbine engine applications due to higher strength-weight ratio at elevated temperatures.Powder metallurgy(PM) offers the potential for solving many of the problems associated with the large ingots, such as center-line porosity and chemical inhomogeneity. In order to study the feasibility of preparing Ti2AlNb special shaped ring with large size, PM + ring rolling combined process is considered as a potential method and discussed in this work. PM Ti2AlNb alloy and special shaped ring(D>800 mm) with a nominal composition of Ti-22 Al-24.5 Nb-0.5 Mo(atomic fraction, %) were prepared from pre-alloyed powder using hot isostatic pressing(HIP). Hot compression tests of PM Ti2 AlNb alloy and wrought alloy with the same chemical composition were conducted on Gleeble-3800 testing machine under 930~1050 ℃and 0.001~1 s-1 conditions. Ring rolling was conducted on PM Ti2 AlNb special shaped ring by horizontal rolling machine, and the microstructure evolution and properties performance of PM ring after rolling forming process were studied. The results show that the processing window for PM Ti2AlNb alloy is broader than that for wrought alloys, and wrought Ti2AlNb alloy is easier to crack at low temperature or relative high strain rate. PM Ti2AlNb alloy has more homogeneous chemical composition and uniform α2 phasedistribution. Stress instability phenomenon of PM Ti2AlNb alloy is more obvious than that of wrought alloy which is related to phase transition of Ti2AlNb alloy. Optimized deformation temperature for PM Ti2AlNb special shaped ring was set as 1030~1045 ℃ with reference to the hot compression results. Ti2AlNb special shaped ring after two rolling steps has no any kinds of defects presented by X-ray testing, ultrasonic testing and fluorescence detection. O laths inside PM Ti2AlNb alloy become shorter and narrow, and α2 phase tends to be a coarser and spherical structure due to the hot deformation. After a typical heat treatment(980 ℃, 2 h, AC + 830 ℃, 24 h, AC), nearly B2 + O microstructure is obtained in Ti2AlNb special shaped ring. Compared with the undeformed alloy, tensile ductility at room temperature and 650 ℃ of Ti2Al Nb ring after hot deformation improves due to the refined O phase structure.
作者
卢正冠
吴杰
徐磊
崔潇潇
杨锐
LU Zhengguan;WU Jie;XU Lei;CUI Xiaoxiao;YANG Rui(Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China;School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第6期729-740,共12页
Acta Metallurgica Sinica
关键词
TI2ALNB
粉末冶金
热等静压
环轧成形
Ti2AlNb
powder metallurgy
hot isostatic pressing
ring rolling forming
