【作者】 陈杏芳；

【导师】 张澜庭；

【作者基本信息】 上海交通大学 ， 材料工程， 2012， 硕士

【摘要】 针对Nimonic 80A叶片材料供货质量不稳定的情况,及晶粒结构对材料蠕变持久性能的影响,对该材料的成型、热处理等制造过程中的微观组织演变情况进行分析,得出了复杂晶粒度形成机理及其影响因素。本文主要对材料热处理过程及锻造过程进行模拟,考察其对晶粒结构的影响。采用热模拟机Gleeble 3500对锻造工艺进行模拟,变形温度为1000℃到1150℃,变形量为0.22到1.61,变形速率恒为1s-1。采用OM以及背散射电子衍射方法(EBSD),对热变形过程中的动态再结晶(DRX)微观机制,进行了进一步的探讨;采用EBSD, Image-Pro Plus, Origin等手段,系统研究了热变形条件对晶粒度分布的影响规律;热变形过程中的孪晶演变规律也通过EBSD进行了研究。最后得出了晶粒结构与热变形条件的关系图,总结出了均匀晶粒度分布与复杂晶粒度分布对应的热变形条件。研究了原始均匀样品经过不同热处理制度,温度从1060℃到1150℃,热处理时间从2分钟到60分钟,然后水冷,之后显微组织的变化。通过金相分析(OM),发现在1080℃/60分钟、1100℃/8分钟、1120℃/4分钟出现了异常晶粒长大(AGG);而在1060℃下,2到60分钟没有发现明显的晶粒长大;在1150℃/2分钟晶粒就发生了明显的长大,没有异常长大晶粒。同时通过扫描电镜背散射电子成像分析,得出了1120℃下,随加热时间变化,碳化物的分布演变,探讨了其对AGG的影响规律。更多还原

【Abstract】 Because of the unstable quality of the supplied products for Nimonic 80A used for blades materials, and the great influence of grain structure on the creep resistance of materials, analysis of microstructure evolution during processings such as forging and heat treatment was conducted. Through this study, the mechanisms of complex grain size distribution and its related factors were concluded.In this paper, simulation of the processing such as forging and heat treatment were done to examine its influence on the grain structure.Use Gleeble 3500 to simulate the process of forging. Temperature of hot deformation is from 1000℃to 1150℃, and the true strain is from 0.22 to 1.61, with constant strain rate of 1s-1. Investigate the mechanism of dynamic recrystallization (DRX) during hot deformation with optical microscopy (OM) and electron backScatter diffraction (EBSD) in detail; Study the influence of hot-deformed condition on the grain size distribution systematically with EBSD, Image-Pro Plus and Origin. Besides, the behavior of twinning boundary during hot deformation was also studied with EBSD. In the end, the relationship between grain structure and condition of hot deformation was obtained.Study the microstructure evolution after different heat treatments, with temperatures from 1060℃to 1150℃, time from 2 minutes to 60 minutes and then water cooled. Through OM, abnormal grain growth (AGG) was found in the condition 1080℃, 60minutes, 1100℃, 8 minutes and 1120℃, 4 minutes; while at 1060℃, there is no AGG after 60 minutes; grains have shown apparent growth after 2 minutes at 1150℃. Meanwhile, investigation of carbides distribution with the variation of time at 1120℃with backscatter electron image (BSE) was conducted to study its influence on AGG.更多还原