冷轧TA18钛合金管材退火织构的形成机制

Formation Mechanism of Annealing Texture of Cold Rolled TA18 Titanium Alloy Tube

摘要:

TA18钛合金管材因使用环境要求应具有特定的径向基面织构,退火温度是其重要影响因素之一,为了揭示管材退火织构的形成机制,文章选取Φ8×0.6 mm冷轧管材以及经450、500、550、600、650、700、750 ℃/3h等温度退火管材为实验材料,利用电子背散射衍射(EBSD)技术研究了管材晶粒在不同退火温度下的取向特性。结果表明：初始冷轧管材具有较强的径向基面织构,且<10-10>晶向主要平行于管材轴向；管材在450～550 ℃、550～650 ℃、650～750 ℃退火时分别发生了回复、再结晶及晶粒长大,管材织构的转变主要发生在再结晶及晶粒长大阶段,随着再结晶的发生,管材径向织构不断增强,再结晶后的<11-20>晶向主要平行于管材轴向。再结晶退火使管材径向织构增强的主要原因是,原冷轧管材中的细小晶粒具有比基体更强的径向取向,再结晶晶粒优先在这些细小晶粒处形核生长,并获得了强径向取向,在随后的晶粒长大过程中,这些强径向取向晶粒不断长大并占据优势,从而使管材表现出强径向分布的“再结晶织构”。

关键词:TA18钛合金;再结晶退火;织构;Kearns系数

Abstract:

TA18 titanium alloy tube has specific radial basal texture due to the requirement of its service environment and the annealing temperature is one of the important factors. In order to reveal the formation mechanism of annealing texture of the tube. In this paper, Ф8×0.6 mm the cold rolled tube and the annealed tube at 450, 500, 550, 600, 650, 700, 750℃/3h were selected as experimental materials. Studied the grain orientation characteristics of the tubes at different annealing temperatures by electron backscatter diffraction (EBSD). As a result, the cold rolling tube had great radial basal texture and <10-10> direction was mainly parallel to the axial direction of tube. The grain recovery, recrystallization and growth occurred at annealing temperature 450-550℃,550-650℃,650-750℃ respectively and the transformation of texture occurred during the stage of grain recrystallization and growth. With the occurrence of recrystallization, the radial texture of tube was enhanced and the <11-20> direction was mainly parallel to the axial direction. The main cause of radial texture enhancement is that the fine grain of original cold rolling tube had more obvious radial orientation than the matrix, and the crystallization grain was prior to nucleation and growth around the fine grain and obtained strong radial orientation. During the following process of grain growth, the grain with strong radial orientation can grow dominantly, so that the tube can perform obvious radial distributed ‘recrystallization texture’.

Key words:TA18 titanium; Recrystallization annealing; Texture; Kearns factor