Study On The Texture Of TA18 Titanium Alloy Tubes

TA18 titanium alloy (Ti-3A1-2.5V) was first developed in 1950s in the USA for the pressure charging system in the airplanes. TA18 titanium alloy is aα+βtitanium alloy which is near a phase. This alloy is an ideal material for making tubes because it has good mechanical property both in low and high temperatures,good corrosion resistance,excellent plastic and welding property. But the texture will arise in the tubes during the course of manufacturing procedure, which will lead to the anisotropic property and reduce of the processing property. For this reason, how to improve the property of TA18 titanium alloy tubes by controlling the processing parameters is an important research subject of this alloy.The texture of different types of TA18 titanium alloy tubes was studied by means of X-ray diffraction and electron backscattered diffraction (EBSD). Pole figure and orientation image were introduced to characterize the texture in the tubes. Besides, the date measured from X-ray diffraction was used to calculate the Kearns factors and CSR values, at the same time, Kearns factors and CSR values were also calculated with the date from electron backscattered diffraction, the result will help to analyse the mechanical property and improve the property of TA18 titanium alloy tubes by controlling the processing parameter.The result shows that preferencial orientation of the grains was observed in TA18 titanium alloy tubes after the process of rolling, the basal plane of the grains distributed in the plane of RD-TD, the majority the c-axis of the grains deflected 30～40°from the ND direction. Radial texture is the principal texture in the tubes with a proportion of 0.6, while the circumferencial texture and longitudinal texture is relatively small. Besides, the method of calculating Kearns factors and CSR values is an effective way to characterize the texture of TA18 titanium alloy tubes, the CSR values of most TA18 titanium alloy tubes calculated from X-ray diffraction match the reslut calculated from EBSD very well, but the result of the sample with a high circumferencial texture calculated from X-ray diffraction is not accurate. The result calculated from EBSD is credible.After getting the Kearns factors and CSR values, the effect of processing technique on the texture and property of the tubes was discussed with the date of mechanical and processing property. The result shows that properly increase the deformation degree and Q value will help to acquire radial texture. The texture of imported TA18 titanium alloy tube was measured too, the result shows that radial texture in imported tube is stronger than that in the preproduction tubes, while circumferencial texture is lower than the preproduction tubes. The fr is 0.665, ft is 0.241. It is estimated that the imported tube went through a large deformation and Q value then got strong radial texture and low circumferencial texture. The fact is that the formation of texture in the tubes is the result of many variable parameters, properly adjusting the parameters is the way to improve the property of the tubes.