Research On Superplasticity Of LD10 Alloy And Ti-10V-2Fe-3Al Powder Alloy

Titanium and aluminum alloys, which are nonferrous alloys, have considerable strength-to-weight advantage over comparable-strength steels. Therefore, they have been found in wide use in aerospace industry. It is of great significance to research on the superplastic properties of these alloys for using superplastic isothermal forging to manufacture complex forge pieces.In this paper, equiaxed fine-grained structure can be obtained when 16mm diameter hot-rolled bars of LD10 alloy are pretreated via proper recrystallization annealing (temperature 420℃). The average elongation is increased from 158.2% to 223%, and the process is the optimal pretreatment in this paper. In addition, equiaxed fine-grained structure and better superplasticity can also be obtained when the hot-rolled bars are pretreated via proper recrystallization annealing (temperature 380℃, 460℃) and solution annealing (temperature 500℃). And the maximum elongation is 321% in individual specimen.The tensile specimens through annealing at 420℃ present superplasticity (elongation 108%~231%), in the range of temperature from 460℃ to 510℃ and the strain rate from 1.1x10-2s-1 to 1.1x10-4s-1. The optimal superplastic deformation condition is 500℃~510℃ and 3.3x10-4s-1, on which the average elongation is 223%~232% and the flow stress is only 10.389MPa~12.962MPa. The tensile specimens which show better superplasticity appear filaments fracture.The process of powder sintering + isothermal forging is used for Ti-1023 alloy in which the element of Fe is segregated obviously. The relative density can reach 99.57%, homogeneous and fine-grained microstructure can be obtained, the primary a phases are better equiaxed grain and Fe segregation and B spot are completely removed. The tensile property at room temperature get better improved. Therefore the alloy presents excellent superplasticity (elongation 1269%), and the maximum value in individual specimen is 1422%. The process is an effective way to prepare high quality Ti-1023 alloy, to refine the microstructure and improve the superplastic property of the alloy.The experimental result of superplastic tensile test indicates that Ti-1023 powder alloy appear superplasticity (elongation 391%~1269% and 155%~1422% ) in the range of temperature from 700℃ to 820℃ and strain rate from 3.3 X10-4s-1to 3.3 X 10-2s-1. The optimal superplastic deformation condition is 750℃~760℃ and 3.3 X 10-4s-1-3.3 X 10-3s-1, in which the elongation can reach 1269%~1422% and the flowstress is 23.6Mpa~62.3 Mpa. Under optimal superplastic deformation condition the tensile specimens fracture in the form of point and the fracture surface fluctuates greatly. It shows obvious intergranular fracture.