(1. 上海大学 省部共建高品质特殊钢冶金与制备国家重点实验室,上海 200444; 2. 上海大学 材料科学与工程学院,上海 200444; 3. 中国科学院 金属研究所,沈阳 110016; 4. 上海大学 材料基因组工程研究院,上海 200444)
摘 要: 通过相场法研究了1073K时效过程中Ni-Al高温合金γ′相的析出动力学。结果表明:在形核长大阶段,随Al成分增加,γ′相的生长动力学指数m值总体呈下降趋势,当ρ≈0.5(ρ为γ′相半径与平均半径的比值)时,γ′相数目达到最大,小于该尺寸的γ′相几乎不存在。在γ′相的粗化阶段,γ′相的生长动力学指数m值介于2~3之间,γ′相的生长机制为溶质扩散与界面迁移共同作用的混合机制。粗化阶段γ′相的尺寸分布符合Gamma分布,且粗化后期满足标度律。在γ′相的粗化后期,随时间的延长,γ′相的尺寸均匀性越好,且随Al成分增加,γ′相的粗化机制有从溶质扩散机制向界面迁移机制的过渡。
关键字: 镍基高温合金;相场法;析出动力学;生长机制;动力学指数
(1. State Key Laboratory of Advanced Special Steel, Shanghai University, Shanghai 200444, China; 2. School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China; 3. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; 4. Institute of Material Genome, Shanghai University, Shanghai 200444, China)
Abstract:The kinetics of the γ′ phase precipitation for Ni-Al superalloys at 1073K was studied by the coherent phase-field method. The results shows that, at the nucleation and growth stages, as the Al composition increases, the kinetic exponent m of γ′ phase growth shows an overall declining trend. It is difficult to determine the growth mechanism of the γ′ phase. According to the γ′ phase size distribution at the nucleation and growth stages, it is known that the number of γ′ phase particles reaches the maximum near ρ=0.5 (ρ is the ratio of γ′ phase radius to its average radius). The particles with size smaller than ρ=0.5 are much less. During the coarsening stage, the range of m value is between 2 and 3. The growth mechanism of the γ′ phase is hybrid comprised of the solute diffusion mechanism and the boundary migration mechanism. The size distribution of γ′ phase at the coarsening stage approaches the Gamma distribution and satisfies the scaling rule at the late period of coarsening. Besides, as the Al composition increases, γ′ phase size becomes more uniform and γ′ phase coarsening mechanism changes from the solute diffusion mechanism to boundary migration mechanism.
Key words: Ni-based superalloy; phase-field method; precipitation kinetics; growth mechanism; kinetic exponent