Effect of crystallographic orientation on globularization during the rolling of a near α titanium alloy tube
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摘要: 研究了一种近α钛合金管在热轧过程中发生的动态球化规律。通过金相组织分析和电子背散射衍射（EBSD）技术对管材外表面附近和中间部位进行观察，结果发现：在热轧过程中，管材外表面附近的α相球化率很高，球化后的组织大角度晶界变多而小角度晶界变少；中间部位的α相球化程度受晶体学位向影响很大。通过计算不同晶体学取向α相的施密特因子，发现基面滑移和柱面滑移在轧向（RD）和弦向（TD）均有较大的施密特因子（>0.3）时，很容易发生球化。当α相仅有一种滑移系且仅在一个方向有较大的施密特因子时，则很难被球化。Abstract: The dynamic globularization of a near α titanium alloy tube during hot rolling was studied by observation of different regions of the pipe using metallographic analysis and electron backscatter diffraction (EBSD) technology. The results showed that the fraction of globularized α phases near the outer surface of the tube was very high. After globularization, the large-angle grain boundaries increased and the small-angle grain boundaries decreased. The globularization of the α phases in the middle part was greatly affected by the crystal orientation. The Schmidt factor of α phase in different crystallographic orientations is calculated. It was found that the α phases were more prone to be globularized when the basal slips and prism slips have a larger Schmidt factor (> 0.3) in the rolling direction (RD) and transverse direction (TD), respectively. The globularization would be difficult when the α phase has only one slip system and the Schmidt factor was high only in one direction.
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Key words:
- titanium alloys /
- tube /
- hot rolling /
- microstructures /
- globularization /
- crystallographic orientations
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图 3 管材纵截面不同部位的微观组织
Figure 3. Microstructure of different parts of the longitudinal section of the tube
图 4 不同区域的再结晶晶粒分布情况
Figure 4. Distribution of recrystallized grains in different regions
图 6 管材不同区域的TD方向的EBSD反极图
Figure 6. The inverse pole figures in TD direction in different regions of the tube
表 1 钛合金管材的实测成分
Table 1. Chemical compositions of Ti80 pipe
% Ti Al Nb Zr Mo Si Fe C N O 87.614 6.12 3.1 2.07 0.94 0.03 0.02 0.005 0.001 0.10 
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表 2 不同晶粒在不同应变方向下的施密特因子
Table 2. Schmidt factors of different grains in different strain directions
滑移系 施密特因子 A1 A2 A3 B1 B2 B3 B4 基面滑移
{0001}RD 0.32 0.08 0.06 0.28 0.05 0.34 0.02 TD 0.35 0.34 0.10 0.37 0.36 0.27 0.05 柱面滑移
{10-10}RD 0.42 0.49 0.31 0.45 0.46 0.31 0.19 TD 0.50 0.28 0.20 0.40 0.08 0.41 0.45
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