α-β型チタン合金の組織制御を施した素粉末混合法による高性能化

概要

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A variety of α-β titanium alloys were produced by the microstructure-controllable new Blended Elemental (BE) P/M method, in which as-sintered material is water-quenched from the β-phase region prior to HIP'ing, with emphasis on relating composition/processing/microstructure to mechanical properties. Alloy composition was found to have a strong effect on the microstructure. In near a type α-β alloys such as Ti-6Al-2Sn-4Zr-2Mo, the new BE method created a fine two phase structure in a relatively small β grain with lower aspect ratio α-platelets. This microstructure resulted in improved high cycle fatigue strength compared to those for conventional BE alloy. In contrast, in β-rich α-β alloys such as Ti-5Al-2Cr-1Fe, a massive α phase was formed on prior β grain boundaries. In this case poor improvement in fatigue strength was obtained because of the presence of this massive α. High temperature mechanical tests done on near a type alloys revealed that both creep resistance and low cycle fatigue strength were superior in new BE material than in conventional BE material. These findings demonstrated that the new BE method applied to near a type α-β alloys can give rise to better balance of mechanical properties compared with that of ingot metallurgy.
社団法人日本鉄鋼協会の論文
1991-12-01