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Microstructure and Deformation of Ti-22Al-23Nb Orthorhombic-Based Monolithic and Composite Titanium Aluminides

Published online by Cambridge University Press:  15 February 2011

François-charles dary ,
Shiela R. Woodard  and
Tresa M. Pollock
François-charles dary
Affiliation:
Current address: Materials Dept., University of California, Santa Barbara, CA 93106
Shiela R. Woodard
Affiliation:
Materials Science and Engineering Dept., Carnegie Mellon University, Pittsburgh, PA 15213
Tresa M. Pollock
Affiliation:
Materials Science and Engineering Dept., Carnegie Mellon University, Pittsburgh, PA 15213
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Abstract

A new class of intermetallic matrix composites (IMC's) based on orthorhombic titanium aluminides offer attractive properties for high-temperature structural components at temperatures up to 760°C. Results from an ongoing study on the microstructural stability and mechanical properties of the orthorhombic-based alloy Ti-22Al–23Nb (at%), in both monolithic and composite forms, are discussed. Oxygen acquired during processing or as a result of high-temperature exposure in air or vacuum has a pronounced influence on the microstructure of the monolithic and composite materials. Two-phase lath microstructures of ordered beta (βo) + orthorhombic (O) phases produced by processing low oxygen material above the beta transus are morphologically stable at 760°C. Conversely, in higher-oxygen three-phase microstructures containing O+βo+ α2(Ti3Al), lath coarsening and additional precipitation of α2 in oxygen-enriched sheet surface regions is observed. At 760°C/69MPa the two-phase lath microstructure has a higher creep resistance and lower tensile strength compared to the three-phase α2- containing microstructures of the higher oxygen material.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 350: Symposium U – Intermetallic Matrix Composites III , 1994 , 279
Copyright
Copyright © Materials Research Society 1994

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