Methods for processing titanium aluminide intermetallic compositions

Abstract

Methods of processing compositions containing titanium and aluminum, especially titanium aluminide intermetallic compositions (TiAl intermetallics) based on the TiAl (gamma) intermetallic compound. The methods entail processing steps that include a hot isostatic pressing (HIP) cycle and a heat treatment cycle that can be performed in a single vessel. TiAl intermetallic compositions processed in this manner preferably exhibit a duplex microstructure containing equiaxed and lamellar morphologies.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 614,751, filed Mar. 23, 2012, the contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]The present invention generally relates to compositions containing titanium and aluminum and the processing thereof. More particularly, this invention relates to methods of processing cast titanium aluminide intermetallic compositions that entail hot isostatic pressing and heat treatment to close porosity and yield a desirable microstructure.[0003]Because weight and high temperature strength are primary considerations in gas turbine engine design, there is a continuing effort to create relatively light weight alloys / compositions that have high strength at elevated temperatures. Titanium-based alloy systems are well known in the art as having mechanical properties that are suitable for relatively high temperature applications. High temperature ca...

AI Technical Summary

Benefits of technology

This patent describes how to create desirable microstructures in titanium-aluminum intermetallics that are difficult to achieve through traditional methods. The invention also allows for the use of energy during cool-down from a specific process to assist with a subsequent heat treatment, which can eliminate the need for additional pre- and post-heat treatment cycles. These technical effects have been particularly observed with net-shaped castings produced by net-shape casting methods, but other titanium-aluminum intermetallic compositions can also benefit from the processing methods provided by the invention.

Problems solved by technology

Another technical effect is the ability to take advantage of the energy available for phase equilibration during cool down from a HIP step to assist in a subsequent heat treatment, which has been determined to eliminate the requirement for conventional pre- and post-heat treatment cycles that may cause aluminum to be lost from the casting surface as well as incur additional cost and cycle time.

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