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The Influence of Processing Variables on the Structure and Properties of Extruded Beta III Titanium.
Technical rept. Mar 68-Jul 70,
AIR FORCE MATERIALS LAB WRIGHT-PATTERSON AFB OH
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The extrusion temperature and cooling rate after extrusion were varied for round to round axisymmetric extrusions of the Beta 111 titanium alloy. The microstructures after extrusion and after heat treatment were examined both by optical and transmission electron microscopy and correlated with the room temperature mechanical properties. Heat treatment following extrusion consisted of either aging only or a solution treatment followed by aging. In contrast to air cooling after extrusion, direct water quenching immediately after extrusion was effective in retaining a significant amount of dislocation structure from the hot deformation, the effect being greater at the lowest extrusion temperature. This retained dislocation structure effectively promoted the formation of alpha during aging and retarded the tendency for the omega phase to form. The effect was greatest when specimens were aged without the intermediate solution treatment. The greater amount and finer distribution of alpha obtained in this manner resulted in significantly higher tensile strengths, quite acceptable values of RA, but with a small loss in fracture toughness. For the extrusion temperature range investigated, the extrusion pressures for the Beta 111 titanium alloy were somewhat lower than for the older, more well established beta titanium alloy. he extrusion pressures for Beta 111 were also lower than for alpha and alpha plus beta titanium alloys, for temperature ranges where they have significant amounts of alpha present. Author
APPROVED FOR PUBLIC RELEASE