抗氢合金J75中低∑CSL晶界的形成与演化

Formation and Evolution of Low∑CSL Grain Boundaries in J75 Hydrogen-Resistant Alloy

以铁镍基抗氢合金J75为研究对象,采用单步形变热处理和电子背散射衍射(EBSD)技术,研究了低∑CSL晶界的形成和演化过程。结果表明:采用5%预变形+1000℃退火的单步形变热处理方法,可将J75合金中低∑CSL晶界的比例提升至70%以上,形成具有∑3n取向关系的晶粒团簇;退火过程中,低∑CSL晶界比例的提升主要是由于∑3n界面比例的提升,其中∑3占绝大比例。发现一种∑3再生过程,其机制在于:由于∑3ic迁移能力强,在退火过程中与其他∑3相遇会形成∑9晶界,而∑9与∑3相遇,倾向于发生∑9+∑3→∑3,导致∑3的再生;不连续大角度随机晶界(R)与低∑CSL晶界相遇会形成R/∑晶界,当R/∑晶界为低∑CSL晶界时,则构成较多具有低∑CSL晶界的网络,打断了R晶界的连通性。

The researches in the area of grain boundary engineering were mainly focused on the relationship between process,microstructure and properties.However,little attention had been paid to the formation and evolution process of low∑CSL grain boundaries.To better understand the dynamic process,electron backscatter diffraction(EBSD)was used to analyze the grain boundary migration and evolution in J75 alloy.Single-step deformation heat treatment with 5%pre-deformation and 1000°C annealing was used to increase the proportion of low-∑CSL grain boundaries to over 70%,and formed grain clusters with∑3 n orientation relationship to break the connectivity of random grain boundaries.During the annealing process,the migration ability of∑3 ic was strong,and when it encountered other∑3,∑9 would be formed;in addition,∑3 with∑9 would lead to∑3+∑9→∑27 or∑9+∑3→∑3 processes,and the latter was more likely to occur.The∑3 regeneration was closely related to the∑3 ic grain boundary;a mechanism for breaking the connectivity of random grain boundary network was proposed.When random grain boundary met low∑CSL grain boundary,R/∑would form.If the ratio(R/∑)≤29,the connectivity of random grain boundaries network could be interrupted.