Development of titanium metal matrix composite exhaust valve

摘要

In October 1998, a new mass-produced car with titanium engine valves (both intake and exhaust) become available from the Toyota Motor Corporation. Both the intake and exhaust valves were manufactured via a newly developed cost-effective powder metallurgy process. Furthermore, the material, which was specially designed based on the mechanical properties of the exhaust one, is a unique TiB reinforced titanium metal matrix composite (MMC). This paper discusses the materials and manufacturing methods used. The tensile strength, the high-cycle fatigue strength and the creep resistance of the MMC from room temperature to 800°C are always superior to those for the typical 21-4N heat4esistant steel and Ti-1100 (heatresistant Ti Alloy). These properties have been realized by the best combination of a special heat-resistance titanium alloy and the ideal reinforcement particle, TiB. Both valves have achieved sufficient durability and reliability with a manufacturing cost acceptable for mass-produced automobile parts. The new engine using the developed titanium-based exhaust and intake valves reduced the valve weight by 40% and the valve spring by 16%. As a result, the maximum revolution increased by 10% and the noise in the high revolution range decreased by 3dB.