Production of High Strength Titanium Alloy through HIP

Abstract

A pre-alloyed powder metallurgy method has been investigated in order to produce high-strength titanium alloy at a lower cost than by currently executed blended elemental powder method. Ti-6Al-4V alloy bars containing 3.5 %Fe and 4 %Cu of ϕ 22 mm were produced using Ti-6Al-4V alloy powder as a starting material by hot isostatistic pressing (HIP) followed by forging and hot-rolling. The material densified to almost 100 % density through HIP process. Microstructure after hot rolling at the temperature of (α + β) region showed fine equi-axial grains. Tensile characteristics of Fe and Cu containing alloys were strongly influenced by heat treatment condition. Just after hot rolling or heat treatment, especially air-cooling, the addition of Fe and Cu resulted in high strength but poor elongation. Water-cooled material showed enough elongation but a little bit poorer strength. These tensile characteristics seem to be explained by the β phase ratio in the alloy. This result shows that tensile properties of Ti-6Al-4V alloys containing Fe and Cu can be controlled by heat treatment condition, and possess high potential in the application for airplane and automobile.