Microstructure And Properties Of CP-Ti Plates Processed By Equal Channel Angular Pressing

Equal channel angular pressing(ECAP) technique can produce ultrafine-grained materials and improve the mechanical properties of materials. Commercially pure titanium plate was successfully processed by equal channel angular pressing for 1~8 passes via route C at room temperature using a channel angle Φ=135°. Microstructural evolution and macrotexture of pure titanium plate after ECAP were analyzed by OM, TEM and XRD. The thermal stability of ultrafine-grained titanium plate was investigated through annealing experiment, and the mechanical properties of the materials were tested by tensile and hardness tests.The results show that the grains are gradually elongated and broken and lots of dislocations and twins form during the initial stage of ECAP. With numbers of passes increasing, the interactions between dislocations make dislocation density deceasing gradually. The low angle grain boundaries gradually evolve into high angle grain boundaries which form ultrafine grains with average grain size of about 0.67 μm.Hardness and ultimate tensile strength of CP-Ti plate are significantly improved after 8 passes of ECAP. The hardness of X, Y, Z planes of specimens is up to 1910 MPa, 1943 MPa and 1911 MPa, respectively, and the ultimate tensile strength increases to 682 MPa, which is improved 98.8%. With increasing the numbers of passes, the elongation to fracture decreased rapidly and then recovered slowly.Ultrafine-grained pure titanium plates were annealed at 150℃~500℃ for 1h. The results show that the effect of annealing temperature on the mechanical properties of the materials is significant. With increasing annealing temperature, the microhardness and ultimate tensile strength decrease gradually and elongation to fracture increases.The initial texture of pure titanium plate is prismatic texture. With increasing the numbers of passes, shear texture forms and its intensity increases gradually.