It is a widely use of titanium alloys in the industrial production fields because of their unique high strength-weight ratio, fracture resistance, and superior resistance to corrosion. An increasing number of companies prefer to use Titanium alloy TC11 instead of TC4 in manufacturing impellers and blades, due to the better combustion resistance property and the ability of working in high temperature for a long time. Titanium alloys are classical difficult-to-machine materials for their inherent high strength maintained at elevated temperature and low thermal conductivity leading to high cutting temperatures. For some aero-engine components, such as impellers, which have twisted surfaces, it is difficult to satisfy the higher and higher surface quality requirements by just using milling operation.
In an automotive internal combustion engine, a turbocharger rotor has contributed to the increment of both the power efficiency and the fuel reduction, because the exhaust gas promotes the intake efficiency without additional fuel consumption. However, the turbocharger rotor has a fatal drawback called ‘‘turbo-lag’’ which delays the steady state operation of turbocharger under 2000 rpm. Titanium aluminides can reduce the weight to a half of the conventional turbocharger. Besides, TiAl alloys have the combination of low density, high specific strength, excellent mechanical properties, and heat resistance. Accordingly, TiAl alloys can eliminate the turbo-lag problem. Until now, for manufacturing of turbocharger, powder metallurgy and casting process have been incorporated. However, it is hard to apply powder metallurgy process to turbocharger manufacturing, due to its poor soundness and weldability.
From the viewpoint of cost-effective process, investment casting could be regarded as an economic net-shape technology for TiAl alloys. However, the turbocharger has both the curvature and thin wall parts, and there is no proper information such as castability and fluidity with mold temperature, melt temperature and centrifugal force. The modeling of casting offers a powerful and cost-efficient way to study the effectiveness of various casting parameters.
Reference
Loria EA. Gamma titanium aluminides as prospective structural materials. Intermetallics 2000;8:1339e45.
Post time: May-30-2022