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Numerical Simulation of Isothermal Forming of TiAl-Based Alloy

Author: DengTaiQing
Tutor: HuLianXi
School: Harbin Institute of Technology
Course: Materials Processing Engineering
Keywords: tial based alloy high temperature flow stress model isothermal forging numerical simulation
CLC: TG146.23
Type: Master's thesis
Year: 2009
Downloads: 77
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Abstract


TiAl based alloys are widely studied because their light weight and excellent elevated temperature properties such as high strength retention, resistance to creep and oxidation. However, their application is currently limited by the poor ductility and strong resistance to deformation at elevated temperature. To understand the deofrmation behavior and the effect of process parameters on deformation of the Ti-47Al alloy during high temperature forming and decrease wasting of time, man power and cost, It is well known that FE technology is a perfect method and has played important part in the study on the metal forming processes, which can provide scientific foundation for predicting whether defects occurring or not and determining the optimal process parameters.In this paper, Based on the hot compression experimental study at isothermal constant strainrate and the Orthogonal experiment, the influence of deformation temperature, strain rate and strain on flow stress has acquired in hot deformation process of Ti-47Al alloys(atomic ratio). It is found that deformation temperature and strain rate have an notable influence on the flow stress of Ti-47Al alloys, and they are materials sensitive to hot and strain rate. Based on the characteristics of the stress-strain curves of the Ti-47Al alloy during high temperature deformation, a flow stress model of Ti-47Al alloy during high temperature deformation has been established by the stepwise regression method.In the flow stress model, the effcet of these thermomechanical parameters on temperature, strain rate and strain has been taken in to account.Furthermore, the flow stress model is easy to be used. The comparison of the calculated results with the experimental of the test samples shows that present constitutive relationship has a good reliability and can offer the essential prerequisites for improvement of numerical simulation precision of metal forming processes.Based on the developed flow stress interface subroutine program in DEFORM/2D software, a coupled 2D-simulation of deformation with heat transfer has been carried out for the isothermal forging of Ti-47Al alloy. The effect of process parameters, including the deformation temperature, the Punch velocity, the friction and the materials shape on the stress, strain and temperature raise during isothermal forging has been studied and load-journey curves with different thermomechanical parameters has been calculated.The results show that punch velocity and deformation temperature have significant effect on the workpiece forming. This work provides the theory and technique foundation for implementing process optimized design and quality control scheme of Ti-47Al alloy isothermal forging process.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Non - ferrous metals and their alloys > Light non-ferrous metals and their alloys > Titanium
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