Institute of Metals Division - Beta-Titanium Alloys Containing Vanadium, Chromium and Aluminum

The effects of composition on the mechanical properties and aging characteristics of several alloys in the Ti-V-Cr system, with and without aluminum modifications, were evaluated. Increasing the chromium, vandium, or aluminum content increased the strength of quenched structures with chromium being the most effective strengthener. Appreciable aging response was obtained with low chromium alloys, but high chromium alloys age softened rather than. hardened. High vanadium contents had a similar effect. Aluminum additions shifted the aging behavior toward that observed in lower chromium alloys, enabling high chromium alloys to be age hardened. DURING the course of titanium alloy development many a and a-ß alloys have been evolved to commercial status. However, only one all-ß alloy has achieved this same stature. This is the Ti-13V-11Cr-3Al alloy. It is characterized by a very sluggish ß-phase decomposition reaction such that very slow cooling rates can retain the 0 phase at room temperature. In addition, very high strength levels can be obtained by long-time aging treatments. Combinations of cold or warm working followed by aging produce even further improvements in strength. This paper describes the results of a research program in which the effects of composition on the mechanical properties and aging characteristics of several alloys in the Ti-V-Cr system, with and without aluminum modifications, were evaluated. EXPERIMENTAL PROCEDURES Electrolytically refined, high-purity titanium was used as the alloy base for these studies. Iodide chromium, electrolytically refined vanadium granules, and high-purity aluminum sheet were used as alloying additions. The compositions of interest were melted as 250-g ingots in a direct current arc melting furnace under a flowing atmosphere of argon. The ingots were hot forged to 3/4-in.-diam bars, vacuum annealed for 6 hr at 1800°F to reduce residual hydrogen content, and then hot swaged to 1/4-in.-diam rods. Fabrication history, and interstitial analyses after fabrication are given in Table I. All specimens to be heat treated were sealed in Vycor capsules under a partial pressure of argon. Samples used to define the ß transus were quenched from temperatures ranging from 1350° to 1100°F after holding at temperature for 15 min. Samples for aging studies were quenched from above the ß transus temperature and then aged for up to 64 hr at 750°F and for 100 hr at 850°, 900°, and 950°F. The effects of straining prior to aging were also investigated. The results of these studies were used to select the heat treatments for the tensile specimen blanks. Heat treatments of the tensile specimens are described in Table 11. Alloys were aged after solution heat treatment or after solution heat treatment and cold swaging to 50 pct reduction in area. Standard 0.125-in.-diam tensile specimens were machined from the heat-treated blanks. All tensile tests were performed in a Baldwin-Southwark uni-