素粉末混合法 Ti-6Al-4V 合金の組織制御による機械的特性の改善(<特集>チタンおよびチタン合金)

概要

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Despite the attractiveness of high strength-to-weight ratio of titanium alloys, cost problems limit their use in various industrial applications. Blended elemental (BE) titanium powder metallurgy, which uses both press and sinter technique and hot isostatic pressing (HIP) for further densification, offers the greatest cost-saving potential, but mechanical properties, particularly fatigue, are inferior to those of prealloyed powder metallurgy and ingot metallurgy materials due to the formation of large alpha-platelet colonies and massive grain boundary alpha phase. In the present study, an attempt was made to improve mechanical properties of BE Ti-6Al-4V alloy through microstructural modification. The results of investigation show that the beta solution treatment and water quenching, prior to HIP'ing in the alpha+beta region have a strong effect on the structure modification. This new BE method results in relatively small prior beta grains and produces finear and lower aspect ratio alpha plate structure without formation of grain boundary alpha phase. The resultant mechanical properties are markedly improved over those for conventional BE material, and fatigue strength is as good as prealloyed material.
1986-04-01