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 heat-resistant steel
and Ti-1100 (heat-resistant 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.