Shitoshi Ohtani1 and Minoru Nishigaki1
1Central Research Laboratory, Kobe Steel Ltd., Kobe
Though Ti-15Mo-5Zr shows, as given previously, such excellent characteristics as corrosion resistance, cold workability and weldability, and is placed under several practical applications, the stability and the resistance to oxidation of the alloy is not satisfactory.
With the intention of improving these imperfections of Ti-15Mo-5Zr, the effect of Al addition on the various properties, such as thermal and mechanical stability of beta phase, forgeability, cold workability, aging property, oxidation resistance, and corrosion resistance, were studied. Three Ti-15Mo-5Zr base alloys and three commercial or semicommercial alloys were used in this investigation. Though the embrittlement of Ti-15Mo-5Zr after slow cooling was much reduced by the addition of 3%Al, because Al suppresses and ratards the omega precipitation, Ti-15Mo-5Zr-3Al-2V is superior to Ti-15Mo-5Zr-3Al so far as corrosion resistance is concerned.
The latter alloy showed a marked hardening during the aging at rather high temperature, because Al strengthens the precipitates. This alloy is expected to be an excellent age hardenable alloy for construction application. There was no fundamental difference of oxidation resistance between Al-bearing and Al-free Ti-15Mo-5Zr alloys. The forgeability and cold workability of the alloy was not so much affected by 3%Al addition.
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