摘要
将静电场应用于GH4169合金的时效过程,研究了静电场对合金σ相沉淀析出行为的影响规律,并探讨了其机理.结果表明,合金在850℃以8 k V/cm静电场强度进行15 min时效,σ相开始在晶界析出;时效1 h晶内分布大量γ"相.随时效时间延长,σ相尺寸增大、体积分数增加,γ"相尺寸亦增大.与未加静电场时效处理相比,静电场时效处理后合金中σ相体积分数降低、尺寸减小,γ"相体积分数升高;晶界σ相中Nb原子分数降低、Fe和Cr原子分数升高,晶界σ相点阵常数c减小、a和b增大.由于静电场时效处理后合金中平均空位浓度升高,促进了Fe和Cr原子扩散,同时Fe和Cr原子置换晶界σ相中Nb原子,Nb原子固溶入晶内.另一方面,空位浓度的升高增加了γ"相非匀质形核几率,促进γ"相析出.同时,空位亦可松弛基体γ相与γ"相的共格畸变,有效抑制了γ"相向σ相转变,增加了强化相γ"相的稳定性.
GH4169 alloy is widely used to make aero engine, gas turbine as it is one of the most important superalloy. γ＇＇ phase is the main strengthen phase, however, the metastable γ＇＇ phase will transform to stable d phase during aging or servicing for certain time. σ phase is significance in the alloy, its precipitating and distributing behavior have an effect on the properties of the alloy. In recent year, researchers pay more attention on electric field treatment（EFT）, this is because of high energy density, accurate controlling, clean and safety. EFT is one of the most important energy field except temperature field and stress field. In this work, EFT was performed on GH4169 superalloy to investigate the influence of EFT on precipitation behavior of d phase in the alloy, and the mechanism of the effect of EFT on the phase transformation was also discussed. The results show that d phases precipitate on the grain boundaries after EFT with 8 k V/cm at 850 ℃ for 15 min, and large amounts of γ＇＇ phases precipitate inside the grains. With the increasing of EFT time, both the volume fraction and the size of d phase increase, at the same time the size of γ＇＇ phase increases. The volume fraction of d phase is less and the size of d phase is smaller,and the volume fraction of γ＇＇ phase is higher by EFT, compared with that by aging treatment（AT） for the same time. In addition, the Nb content on the grain boundary decreases and both Fe and Cr content increase, meanwhile the lattice parameters of c decreases and a, b increase. The vacancy concentrations can be accelerated by EFT, so that the diffusion of Fe and Cr atoms can be promoted. Meanwhile, the Nb atoms in d phases on the grain boundaries can be displaced by Fe atoms and Cr atoms, therefore the Nb atoms are dissolved into the grain. The nucleation rate of γ＇＇ phases increases with the increasing of vacancy concentrations. The vacancies relax coherent distortion between g phases and γ＇＇ phases, and suppress γ＇＇ phases to transform to σ phases. Thus the stabilization of γ＇＇ phases is enhanced.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第10期1235-1241,共7页
Acta Metallurgica Sinica
基金
国家高技术研究发展计划项目2012AA03A513
国家自然科学基金项目51171039和51371044资助~~
