W-4Re-0.27HfC合金的1500~1700℃拉伸蠕变性能及损伤机理

Tensile creep properties and damage mechanisms of W-4Re-0.27HfC alloy at 1500~1700 ℃

摘要:

本文研究了粉末冶金制备的W-4Re-0.27HfC合金的拉伸蠕变行为,测试环境为真空,蠕变温度为1500~1700℃,蠕变应力为40~60MPa。采用SEM、EBSD和TEM观察其微观组织,表征晶粒尺寸和位错等组织在蠕变过程中的演变规律。结果表明,W-4Re-0.27HfC合金的稳态蠕变速率范围为1′10-7~5′10-6,较纯钨(W)低两个数量级。W-4Re-0.27HfC合金抗蠕变性能优于纯W主要原因是弥散分布的HfC颗粒钉扎位错和Re取代W原子产生晶格畸变阻碍位错运动,降低位错迁移率。蠕变温度为1500℃时,W-4Re-0.27HfC的蠕变机制以位错滑移为主,伴随有晶界滑动。随着温度升高,位错攀移成为主要蠕变机制。HfC颗粒塞积位错,导致HfC/基体界面结合变差,HfC颗粒剥落出现孔洞,合金蠕变性能下降。

Abstract:

In this paper, the tensile creep behavior in vacuum of W-4Re-0.27HfC alloy prepared by powder metallurgy was studied. The creep temperature was 1500~1700℃ and the creep stress was 40~60MPa. SEM, EBSD and TEM observations were used to observe the microstructure, characterize the evolution of grain size and dislocation during the creep process. The results show that the steady creep rate of W-4Re-0.27HfC alloy ranges from1′10-7~5′10-6, which is two orders of magnitude lower than that of pure tungsten (W). The creep resistance of W-4Re-0.27HfC alloy is higher than that of pure W due to the dislocation pinned by HfC particles and the lattice distortion caused by Re replacing W atoms. The creep mechanisms of W-4Re-0.27HfC is mainly dislocation slip, accompanied by grain boundary slip at 1500℃. Dislocation climb becomes the main creep mechanism with increasing temperature. The dislocations were blocked by the HfC particles, which leads to the debonding of the HfC/ matrix interface. Moreover, the desquamation of HfC particles forms pores, which results in the great degradation in the creep properties of the alloy.