Ultra Fine Grain Preparation and Superplasticity of Ti - 5Al - 3Mo - 1.5V Alloy
Superplasticity is the ability of an alloy to be stretched to very high elongation within a limited range of conditions (grain size, deformation temperature, strain rate). In which, the preparation of ultra fine grain for the alloys is an important condition determining the superplastic effect. The paper presents the cyclic close die forging (CCDF) process to prepare the ultra fine grained microstructure and superplastic properties for Ti5Al3Mo1.5V titanium alloy, which was produced in Viet Nam. The CCDF processes were conducted at deformation temperature of 8500C and the number of cycles from 1 to 3 cycles. The average grain size is obtained about 1 ÷ 2 µm. Tensile tests of the alloy after the CCDF process were performed at deformation temperature of (800 ÷ 900) 0C and initial strain rates of (10-3 ÷ 9.10-3) s-1. The tensile test results confirm the superplastic deformation ability of Ti5Al3Mo1.5V alloy. In the range of research parameters, the degree of deformation of the tensile specimens can reach large elongation to fracture from over 210 to 1120% with low yield stress.
Keywords- Superplastic deformation; severe plastic deformation; ultra fine grained microstructure; Ti - 5Al - 3Mo - 1.5V alloy