The Study Of Formability And Anisotropy In Commercially Pure Titanium Sheet

Titanium and its alloys have been widely used in aerospace, medical, automative and other fields due to its high specific strength, good biocompatibility, good heat resistance and high resistance to corrosion. Titanium shows intensity anisotropy during forming due to its hexagonal-close-packed(hcp) structure and texture, which restricts the application of titanium. The paper investigated systematically anisotropy in commercially pure titanium sheet with thickness of 0.6mm by tensile tests, forming limit tests, deep drawing and Erichsen tests. In order to reduce the anisotropy, commercially pure titanium sheets with thickness of 3mm were rolled by different rolling routes and different rolling reduction per pass, respectively. The evolution of microstructure and texture during different rolling routes and reduction were investigated by optical microscopy(OM) and X-ray diffraction(XRD). The main research contents and conclusions were as follows:(1)Commercially pure titanium(CP-Ti) sheet exhibited good fomability, the LDR and IE value at room temperature was 2.0 and 10.4mm, respectively. At the same time, CP-Ti sheet showed severe anisotropy during deformation. From rolling direction to transverse direction, ?0.2 increased from 172 MPa to 212 MPa,r value increased from 1.65 to 3.30, ?b decreased from 386 MPa to 288 MPa, ? decreased from 48.3% to 30.2% and n value decreased from 0.195 to 0.081. During deep drawing in the shoulder region reduction ratio in RD, 45° and TD varied slightly, and in the wall region thickening rate in RD, 45° and TD were 34.5%?31% and 15.6%, respectively. The earrings always occurred in 45° direction of cup and earring ratio was 12.3%. The forming limit tests showed that formability in RD was better than that in TD. The Erichsen tests exhibited that crack initiated always along TD.(2)Three different rolling routes were carried out to roll commercially pure titanium sheet from 3mm to 0.9mm in thickness. Texture of the sheet rolled by Route A(rolling along RD), Route B(rolling along TD) and Route C(cross rolling) gradually weakened. The tensile tests showed that samples rolled by Route C had a smaller anisotropy than Route A and B. Compared with Route A and Route B rolled samples, the Route C rolled samples showed a smaller ?r value and a larger r value. The forming performance tests indicated that, during deep drawing, earring ratio of sheet rolled by Route A, B and C were 17.9%, 18.8% and 4.9%, respectively. The IE value of sheet rolled by Route A, B and C were 11.6mm, 12.7mm and 13.6mm, respectively.(3)During cross rolling three different rolling reductions per pass over the range of 0.1-0.3mm were carried out to roll commercially pure titanium sheet from 3mm to 1.4mm in thickness. The XRD results indicated that the sheet showed prismatic texture under three different rolling reduction, but the components of texture varied from rolling reduction per pass. With increasing of rolling reduction per pass, the double-peak texture disappeared. When the rolling reduction per pass was 0.2mm,the sheets showed a smaller anisotropy. The IE value of sheet rolled by three different rolling reductions per pass were 14.4mm, 13.9mm and 14.0mm, respectively.