Reaction zone microstructure in a Ti 3 Al + Nb/SiC composite
- PDF / 3,069,497 Bytes
- 11 Pages / 594 x 774 pts Page_size
- 24 Downloads / 144 Views
I.
INTRODUCTION
D E S I G N S for advanced aircraft and aerospace vehicles are calling for low-density materials with high modulus and strength at temperatures above which currently available materials are not useful. One approach to achieving high-temperature strength is the use of alloys based on high melting point intermetallic compounds. The titanium aluminides, both 0/2 (Ti3AI) and the y (TiA1)base alloys, are receiving much attention lately, but the 0/z alloys seem to be further along in their development. Another approach to increasing both strength and modulus is the composite approach where low-density, highmodulus nonmetallic phases are incorporated into the structure. It has long been recognized that during the consolidation of a composite, interactions can occur between the various components. The nature and extent of this reaction will depend upon the thermodynamic compatibility of the components and the kinetics of the interactions. It is important to understand these reactions, because their products can critically influence the engineering properties of the composite. The purpose of the present investigation was to characterize the reaction zone microstructure of an as-consolidated composite of Ti-25AI-13Nb (atomic percen0 0/2-type matrix with the SCS-6 continuous SiC fiber. This is one of a large number of candidate composite materials being developed for advanced aerospace applications. Our purpose is only to describe the reaction zone. It is hoped that this will eventually help us to understand the influence of the zone on mechanical properties and composite performance. The mechanical properties of this material have been presented elsewhere, tl,2] so they will not be discussed in any detail here. It is noted that earlier studies have examined the reaction zones in composites of Ti and Ti alloys with different
S.F. BAUMANN and S.D. SMITH are with the ALCOA Technical Center, Alcoa Center, PA 15069. P.K. BRINDLEY is with the NASA Lewis Research Center, Cleveland, OH 44135. This paper is based on a presentation made in the symposium "Interfaces and Surfaces of Titanium Materials" presented at the 1988 TMS/AIME fall meeting in Chicago, IL, September 25-29, 1988, under the auspices of the TMS Titanium Committee. METALLURGICAL TRANSACTIONS A
SiC-type fibers, I3,4,51 but to the best of our knowledge, the materials used in the present study have not been examined previously.
II.
EXPERIMENTAL PROCEDURES
A. Fabrication of Composite The composite examined in this work was fabricated by vacuum hot pressing alternate layers of titanium aluminide powder cloth and mats of unidirectionally oriented SCS-6 fibers. The aluminide powder was produced from ingot via the PREP process by Nuclear Metals, Concord, MA, and had the composition shown in Table I. Cloths containing the aluminide powder were prepared by blending the alloy powder with TEFLON* and a stod*TEFLON is a trademark of E.I. DuPont de Nemours & Company, Inc., Wilmington, DE.
dard solution. The blended mixture was heated to drive off the excess s
Data Loading...
