United Technologies Corporation

Martin J Blackburn

Michael P Smith

Daniel F Paulonis

Edgar E Brown

Gary D Linsey

Steven Z Hayden

Anne L D'Orvilliers

Otis X Chen

Robert H Caless

A titanium alloy matrix fiber reinforced composite made from titanium alloy sheet processed to have ductility up to about 35%. Of particular usefulness is the composite having a Ti.sub.3 Al titanium aluminide having this level of ductility. The composites have good resistance to thermal cyclic fatigue.

Ductile titanium alloy matrix fiber reinforced composites

Methods for enhancing the toughness of otherwise brittle powder metallurgy materials are presented. Adding moderate amounts of tough particulate to such brittle material enhances their ductility in excess of that which would be predicted mathematically.

Method for improving the toughness of brittle materials fabricated by

Processing of Ti-6246 for improved mechanical properties including fracture toughness and low cycle fatigue. The process includes beta forging, sub beta transus solutionizing, controlled cooling and precipitation treating.

Method for improving fracture toughness of high strength titanium alloy

Heat treatments are described for improving the fatigue properties of superalloy articles, without adversely affecting other mechanical properties. The entire heat treatment process is performed below the gamma prime solvus temperature so that significant grain growth does not occur. The heat treatment cycle causes the formation of gamma prime particles in a controlled manner and morphology, first at the grain boundaries and then within the grains. The resultant microstructure possesses the benefits of a fine grain structure (improved resistance to fatigue crack initiation) and fine gamma prime particle size (improved resistance to crack growth).

Heat treatment for improving fatigue properties of superalloy articles

The high temperature strength to density ratio of titanium aluminum niobium alloys of the Ti.sub.3 Al (alpha two) type is increased when molybdenum is added. New alloys contain by atomic percent 25-27 aluminum, 11-16 (niobium+molybdenum), 1-4 molybdenum, balance titanium. When vanadium replaces up to 3.5% molybdenum a lighter weight alloy is produced. The new alloys have higher elastic modulus and higher creep strength to density ratio than alloys without molybdenum.

Titanium aluminum alloys containing niobium, vanadium and molybdenum

Cast and forged titanium alloys suited for use at temperatures over 600.degree. C. are based on TiAl gamma phase structure. Useful alloys have about 1.5% or greater tensile ductility at temperatures of 260.degree. C. and below, thereby making them fabricable and suited for engineering applications. Disclosed are alloys having weight percent compositions of 31-36 aluminum, 0-4 vanadium, balance titanium (in atomic percent, about: 45-50Al, 0-3V, bal Ti). The inclusion of about 0.1 weight percent carbon improves creep rupture strength. To obtain high tensile strength, the alloys are forged at about 1025.degree. C. and aged at about 900.degree. C.; to obtain higher creep rupture strength and tensile ductility, a solution anneal at about 1150.degree. C. is interposed before aging.

Titanium alloys of the TiAl type

Titanium-aluminum-niobium alloys having narrow and critical composition ranges are disclosed. The alloys have room temperature tensile elongations of 1.5% or greater and creep strength to density ratios better than certain nickel superalloys. Thus, they may replace other heavier base alloys in many applications up to 750.degree. C. Aluminum content must be closely controlled as excess amount decreases ductility while insufficient amount decreases creep strength. Niobium content is also critical as excess amount adversely affects creep strength-to-density ratio while insufficient amount decreases ductility. And there is an important interrelationship between niobium and aluminum. Disclosed are alloys having atomic percent compositions of 24-27 Al, 11-16 Nb, balance Ti; more preferred are alloys of 24.5-26 Al, 12-15 Nb, balance Ti. (Nominally, these alloys in weight percent are Ti-13/15Al-19.5/30Nb and Ti-13.5/15Al-25/28Nb.) Vanadium is uniquely found to be substitutional for niobium in the foregoing alloys in amounts up to 4 atomic percent, thereby reducing density and increasing strength-to-density ratio while maintaining properties. Mechanical properties are dependent on heat treatment. For the best combination of strength and ductility, the alloys are heated or forged above the beta transus and controllably cooled to produce a fine Widmanstatten microstructure.

Titanium alloys of the Ti.sub.3 Al type

Improved refractories for resisting attack of molten titanium aluminum and similar metals are provided by the inclusion of sulfur. Metal, oxygen, and sulfur combinations, wherein sulfur is present at from 10 to 60 atomic percent, are particularly useful. Disclosed is a material having the atomic formula M.sub.a S.sub.b O.sub.c where O is oxygen, S is sulfur, and M is at least one metal selected from the scandium subgroup of the periodic table transition metals (scandium, yttrium and the rare earths) and aluminum. In an alternate material, M is comprised of at least two elements, the first selected as above and the second selected from the alkaline earth metal group. A preferred material is formed by mixing and firing CaS and Y.sub.2 O.sub.3 in proportions which results in (Ca+Y).sub.0.43 S.sub.0.14 O.sub.0.43.

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Kensington, CT, United States of America

Martin J Blackburn