TC18钛合金锻造过程细晶亮带缺陷的形成机制

Formation Mechanism of Bright-Band Defect of TC18 Alloy During Forging

摘要:

针对TC18钛合金锻坯中的细晶亮带缺陷，采用OM、SEM和EBSD等多种表征方法对其宏微观组织形貌、成分和取向特征等进行了系统分析，并结合Gleeble热压缩研究了细晶亮带缺陷的形成机制。研究表明：TC18钛合金锻坯心部的亮带缺陷对应晶粒尺寸约在100 mm的单个β立方晶粒；锻造过程中由于变形升温导致锻坯心部和边部区域的温度、变形量等存在显著差异，是造成组织不均匀性的重要原因；大尺寸β立方晶粒是由于沿正交方向反复压缩变形，导致锻坯心部<100>织构不断强化，相近取向的<100>晶粒合并形成的；通过退火处理和对角拔长、倒八方等工艺，可以有效地减小和避免细晶亮带缺陷。

Abstract:

A systematical analysis of the macrostructure, microstructure, composition, and crystal orientation of the bright-band defect was conducted by OM, SEM, and EBSD methods, as well as Gleeble tests, and the formation mechanism of bright-band defect of forged TC18 alloy was studied. The results show that the bright-band defects in the center of TC18 alloy forging stocks correspond to β cube-grains with the size of around 100 mm. During the forging process, an inhomogeneous distribution of temperature and equivalent strain in the forging stocks is caused by adiabatic heating, which is an important reason for the microstructural heterogeneity. The large β cube-grains are formed due to the repeated compression along the orthogonal direction, which results in continuous strengthening of the <100> texture in the center of the forging stocks, and the merging of <100> grains with similar orientations. Through annealing treatment and compression along diagonal direction, it is possible to effectively reduce and avoid bright-band defects in TC18 alloy.