近a型钛合金航空锻件宏观清晰晶形成机理及预测模型

doi:10.3901/JME.2021.08.133

摘要/Abstract

摘要： 在双相区锻造成形的某TA15钛合金模锻件表现出局部粗大的清晰晶缺陷。利用金相拼接技术及逐点统计手段对不同晶区的宏微观组织进行分析。研究发现清晰晶区域与模糊晶区域均表现为典型的双态组织。与模糊晶区域对比，清晰晶区域初生等轴α相（α_p）含量略低，次生α相片层略厚且存有大量的粗大原始β晶粒，其平均尺寸可达模糊晶区域的3倍以上。对比研究表明，粗大的原始β晶粒是导致清晰晶缺陷最主要因素，依据试验分析结果给出了锻件出现低倍清晰晶的临界条件。采用模锻件同批次原材料通过热压缩试验，获得了该材料在不同变形条件下宏微观组织的变化规律，进而建立TA15钛合金原始β晶粒尺寸的预测模型，实现了低倍粗晶的可视化预测。研究表明动态相变是造成β晶粒粗化的最主要原因，是导致低倍组织出现清晰晶的根本原因。清晰晶对温度、变形量及应变速率均敏感，当其他条件一定时，变形温度越高、变形量越大及应变速率越小，出现清晰晶的倾向均比较越大。

关键词: 钛合金, 低倍组织, 清晰晶, 预测模型, 动态相变

Abstract: The local coarse and clear grain defects are found in the TA15 titanium alloy die forging formed in the dual phase region. The metallographic stitching technology and point by point statistical method are used to analyze the macrostructure and microstructure of different macro-grain regions. It is found that the microstructure of clear grain region and fuzzy grain region are typical duplex microstructure of the titanium alloy. Compared with the fuzzy grain region, the content of primary equiaxes α phase (α_P) in clear grain region is slightly lower, and the lamellar thickness of secondary α phase is slightly thicker, but there are a lot of coarse original β grains, whose average size is more than 3 times of that of fuzzy-grained region. According to papers, the coarse original β grains are the main factors leading to clear grain defects. The critical condition of clear grain on the surface of the forging is proposed. The same batch of original material is used to perform hot compression tests. The evolvement law variation of macrostructure and microstructure are obtained under different deformation processes. The prediction model of the original β grain size of TA15 titanium alloy is established, so the visualization prediction of macrostructure is realized. The results show that the dynamic transformation can lead to the coarsening of β grain and the clear grain of macrostructure. The clear grain is sensitive to temperature, deformation and strain rate. When other conditions are constant, the higher the deformation temperature, the larger the deformation amount and the smaller the strain rate, the higher the tendency of macrostructure to be clear grain.

Key words: titanium alloy, macrostructure, clear grain, prediction model, dynamic transformation

中图分类号:

TG319

张启飞, 金淼, 陈雷, 张禹森, 杨帅, 郭宝峰. 近a型钛合金航空锻件宏观清晰晶形成机理及预测模型[J]. 机械工程学报, 2021, 57(8): 133-145.

ZHANG Qifei, JIN Miao, CHEN Lei, ZHANG Yusen, YANG Shuai, GUO Baofeng. Formation Mechanism and Prediction Model of Macro Clear Grains in Near α Titanium Alloy Aviation Forgings[J]. Journal of Mechanical Engineering, 2021, 57(8): 133-145.

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