1.Chengdu Advanced Metal Materials Industrial Technology Research Institute Co.,Chengdu 610399,China
2.State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization, Panzhihua 617099,China
TC4ELI titanium alloy plates using for warships were rolled at 1050 and 900 ℃, respectively. The plates had a thicknesses of 40 mm and a width of about 3700 mm. The influence of rolling temperatures on the distribution characteristics of the microstructures and mechanical properties along the normal direction has been researched. Room temperature tensile tests, Charpy impact tests,metallographic analysis and electron backscatter diffraction analysis has been conducted. When rolled at 1050 ℃, there were significant differences in the microstructures and mechanical properties among different thickness areas. The surface areas had lamellar structures consisting of equiaxed α，lamellar α and residual β phases, with higher strength and plasticity but relatively lower impact toughness. The 1/4 thickness and 1/2 thickness areas had lamellar microstructure consisting of lamellar α and residual β phases and conversely had lower tensile strength and plasticity but higher impact toughness. When rolled at 900 ℃, the microstructures of different thickness layers had relatively smaller differences, with bimodal microstructures. The microstructures at surface areas had smaller grain sizes in both primary α phase and secondary α phase, while the microstructures at the central areas had larger grain sizes. Compared with the plates rolled at 1050 ℃, the plates rolled at 900 ℃ had higher tensile strength and plasticity but lower impact toughness, presenting evidence that fine-grain strengthening is the dominant mechanism for TC4ELI titanium alloy plates. In summary, rolling in the α/β phase region is more conducive to improving the microstructures and more effective to improve the uniformity of the microstructures and mechanical properties on throughthickness of TC4ELI alloy plates, compared with rolling in the single β phase region.