Patent Application
20080035250
Like reference numbers and designations in the various drawings indicate like elements.
The exemplary processes of the present invention refine the as-cast or forged grain structure of a titanium alloy through minor additions of boron in the melting stage. With a reduced grain size in the ingot form, the subsequent thermo-mechanical processing (“TMP”), such as converting to billet and then to forging, can be performed in either the beta or alpha plus beta phase fields to produce a final microstructure of fully refined transformed beta grains or a duplex microstructure with fully refined transformed beta grains with fine primary alpha grains. These microstructure refinements improve the fatigue and strength capabilities of the titanium alloy. Furthermore, since the as-cast grain structure may be refined, boron modified titanium alloy based parts may be produced via a casting process.
Referring now to
A quantity of boron sufficient to impart the desired grain refinement may be added to any suitable molten titanium alloy at a step 12. The amount of boron added is preferably tailored to the boron solubility of the molten titanium alloy. Each titanium alloy possesses a boron solubility value, which influences the quantity of boron that may be added. Generally, the solubility of boron in titanium may be less than about 0.05 weight percent of titanium. The quantity of boron typically added is about 0.2 weight percent to about 1.3 weight percent of the molten titanium alloy. Suitable boron sources may include, but are not limited to, AlB12, TiB2, TiB, combinations comprising at least one of the foregoing, and the like. The molten boron-modified titanium alloy may then be cast at a step 14 to form the desired part, component, etc. The resultant boron-modified titanium alloy may comprise the aforementioned titanium alloys and about 0.2 weight percent to about 1.3 weight percent of boron in the form of at least one boride or dissolved boron, or both borides and dissolved boron.
The minor addition of boron in the melting stage refines the as-cast or forged grain structure of the titanium alloy. With a reduced grain size in the ingot form, the subsequent thermo-mechanical processing (“TMP”), such as converting to billet and then to forging, can be performed in either the beta or alpha plus beta phase fields to produce a final microstructure of fully refined transformed beta grains or a duplex microstructure with fully refined transformed beta grains with fine primary alpha grains. These microstructure refinements improve the fatigue and strength capabilities of the titanium alloy. Furthermore, since the as-cast grain structure may be refined, boron modified titanium alloy based parts may be produced via a casting process.
Referring now to
One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
