时效处理对优质GH738合金组织及力学性能的影响

采用力学性能测试与组织观察相结合的方式研究了时效温度和保温时间对优质GH738合金组织及性能的影响规律。结果表明,时效温度和时间均会对γ′相的体积分数和尺寸产生影响。当时效温度在720~800 ℃时,随着时效温度升高,合金强度下降,一次和二次γ′相分别长大30 nm和8 nm,一次γ′相体积分数增加,二次γ′相体积分数减少,时效温度为800 ℃时一次γ′相体积分数达到峰值,约为8%。当保温时间为0~48 h时,随时效时间延长,合金强度先升高后降低,两类γ′相分别长大20 nm和6 nm,一次γ′相体积分数先增后减,二次γ′相体积分数则变化相反。当保温时间为8 h时,两类γ′相体积分数分别达到峰/谷值,含量约为8%和12%。γ′相尺寸和体积分数的变化,特别是体积分数的变化,导致位错的两种强化机制作用效果不同,致使强度发生变化。

Effect of aging treatment on microstructure and mechanical properties of high quality GH738 alloy

Effect of aging temperature and time on microstructure and properties of high quality GH738 alloy was studied by means of mechanical testing and microstructure observation. The results show that the aging temperature and time both affect the fraction and size of γ′ phase. When the aging temperature is between 720 ℃ and 800 ℃, with the increase of aging temperature, the strength of the alloy decreases, the primary and secondary γ′ phases grow up by 30 nm and 8 nm, respectively. The volume fraction of the primary γ′ phase increases, and that of the secondary γ′ phase decreases. When the aging temperature is 800 ℃, the volume fraction of the primary γ′ phase reaches the peak value as about 8%. When the aging time is between 0 and 48 h, with the increase of aging time, the alloy strength first increases and then decreases. The two types of γ′ phase grow up by 20 nm and 6 nm, respectively. The volume fraction of the primary γ′ phase increases first and then decreases, and that of the secondary γ′ phase just changes as the opposite. When the aging time is 8 h, the volume fractions of two types of γ′ phase reach their peak/valley values respectively, as about 8% and 12%. The changes in the size and volume fraction of the γ′ phase, especially volume fraction, lead to different effects of two strengthening mechanisms of dislocations, resulting in change in strength.