Papers by Author: Ying Ying Liu

Abstract: In this paper the effect of isothermal forging process parameters on the microstructure and the mechanical properties of TA15 titanium alloy was researched. The results of the tests indicate that, in the range of temperature of 850 °C~980 °C and deformation degree of 20%~60%, with the increase of temperature or deformation, as the reinforcement of deformation recrystallization, the primary α-phase tends to the spherical shape and secondary α-phase transforms from the acicular shape to fine and spherical shape with disperse distribution, which enhance the tensile properties at room and high temperature. With the increment of forging times, the spheroidization of primary α-phase aggrandizes and secondary α-phase transforms from spherical and acicular shape to wide strip shape, which decrease the tensile properties at room and high temperature. The preferable isothermal forging process parameters are temperature of 980 °C, deformation degree of 60%, and few forging times.

Abstract: The superplastic properties of Ti3Al base alloy have been investigated in the range of 900~1020°C and strain rate range of 3.3×10-4~3.3×10-2s-1 .The largest elongation of 1570% was obtained under the optimal superplastic deformation condition of 980°C and 3.3×10-4 s-1. The m-value varied from 0.46 to 0.59, its maximum value was obtained at 980°C.The microstructure of the alloy after heat treatment was composed of two phases of small spherical α2 phase particles distributing in βtransus matrix. Microstructure change has an obvious effect on the superplastic properties of Ti3Al-based alloy. At 980°C,when theα2 phase grain size changed from large to small then large and the cavitations in the fracture surface were larger and deeper with decreasing strain rate, the alloy showed the larger elongation and the lower flow stress.