新型定向凝固镍基高温合金DZ445中γ'相在高温下的演变规律

Evolution Law ofγ'Precipitates in New Directionally Solidified Nickel-Base Superalloy DZ445 at High Temperatures

通过对新型定向凝固镍基高温合金DZ445进行800~900℃热暴露试验,研究了合金中γ'强化相在高温下的演变规律。结果表明:高温下γ'相的长大受基体元素扩散控制,长大动力学遵循Lifshitz-Slyozov-Wagner熟化规律,扩散激活能为305 kJ·mol^(-1);合金组织稳定,即使是在900℃热暴露10000 h,γ'相颗粒的平均尺寸也只增大至(928±14)nm,在800~900℃下热暴露10000 h时γ'相体积分数保持在50%上下,未观察到拓扑密堆相析出;在850,900℃热暴露过程中,γ'相形貌由类球状向立方或四方块状转变,这种转变与颗粒尺寸和晶格错配度有关。

Evolution law ofγ'strengthening precipitates at high temperatures in a new directionally solidified nickelbase superalloy DZ445 was studied by thermal exposure tests at 800-900℃.The results show that at high temperatures,the growth ofγ'precipitates was controlled by diffusion of matrix elements,and the growth kinetics followed the Lifshitz-Slyozov-Wagner ripening law;the diffusion activation energy was 305 kJ·mol^(-1).The microstructure of the alloy was stable.Even after thermal exposure at 900℃for 10000 h,the average particle size ofγ'precipitates only increased to(928±14)nm.The volume fractions ofγ'precipitates remained about 50%in thermal exposure at 800-900℃for 10000 h,and no topologically close-packed phase was observed.During thermal exposure at 850℃and 900℃,the shape ofγ'precipitates changed from spheroidal to cubic or tetragonal,which was related to the particle size and lattice mismatch.