A high tensile strength above 900? in ?-solidified TiAl alloy through alloy design and microstructure optimization

초록

As a target for high-temperature applications, beta-solidified TiAl alloys have attracted intense attention owing to their low density and superior mechanical properties at elevated temperatures. However, their microstructure instability and the remnant beta o phase in beta-solidified TiAl alloys result in the deterioration of their mechanical properties. In this work, a novel beta-solidified TiAl alloy, Ti-44Al-5.5Nb-0.5W-0.5Cr-0.3Si-0.1C (at%), showing improved high-temperature mechanical properties, was proposed. Appropriate forging and heat treatments were applied to obtain excellent mechanical properties. Hot forging at the (alpha + beta) phase region refined the lamellar colony significantly, and a heat treatment at 1270 degrees C removed the residual beta o phase. Interestingly, undissolved gamma laths contributed to the refinement of lamellar spacing. The optimized sample exhibited a nearly lamellar (NL) structure with a colony size of 38.2 mu m and lamellar spacing of 29.6 nm, thus presenting a tensile strength of 520 MPa at 950 degrees C, indicating the present alloy could be used above 900 degrees C.(c) 2023 Elsevier B.V. All rights reserved.

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