Innovative Processing Techniques for Intermetallic Matrix Composites

Processing Techniques

AbstractAlthough intermetallics based upon aluminum or silicon tend to have a very attractive combination of low density and excellent oxidation resistance, they suffer from lack of adequate creep strength and, in most cases, from inadequate ductility and toughness. It has been recognized for several years that an approach which could simultaneously solve both problems, without degrading other properties, is to utilize the intermetallics as matrices for composite materials. The consequence has been an explosion of interest in two-phase intermetallicbased alloys, as is manifested in the current symposium.

Oxidation of Some Intermetallic Compounds and Intermetallic Matrix Composites

MRS Proceedings ◽

10.1557/proc-364-1339 ◽

1994 ◽

Vol 364 ◽

Cited By ~ 14

Author(s):

M. R. Jackson ◽

R. G. Rowe ◽

D. W. Skelly

Keyword(s):

Intermetallic Compounds ◽

Oxidation Resistance ◽

Matrix Composites ◽

Two Phase ◽

Laves Phases ◽

Composite Systems ◽

Intermetallic Matrix ◽

Intermetallic Composite ◽

AbstractOxidation resistance (1000-1400°C) was characterized for intermetallics M2Al, M3Al, M2Cr, and M5Si3 (M=Nb, Nb+Ti), and metal-toughened intermetallic composite systems. Aluminides were poorest in oxidation, and Laves phases were best. Substitution of Ti for Nb was beneficial for each intermetallic. Addition of metal to produce two-phase castings had differing effects on oxidation, depending on the metal and intermetallic. Modulus and expansion were also measured.

Innovative Processing Techniques for Intermetallic Matrix Composites

MRS Bulletin ◽

10.1557/s0883769400058176 ◽

1990 ◽

Vol 15 (12) ◽

pp. 47-53 ◽

Cited By ~ 15

Author(s):

N.S. Stoloff ◽

D.E. Alman

Keyword(s):

Hot Pressing ◽

Ceramic Matrix Composites ◽

Matrix Composites ◽

Two Phase ◽

Intermetallic Matrix ◽

Phase Intermetallic ◽

Compaction Of Powders ◽

Processing Techniques ◽

Reactive Hot Pressing

Although intermetallics based on aluminum or silicon tend to have a very attractive combination of low density and excellent oxidation resistance, they suffer from lack of adequate creep strength and, in most cases, from inadequate ductility and toughness. It has been recognized for several years that an approach which could simultaneously solve both problems, without degrading other properties, is to utilize the intermetallics as matrices for composite materials. The consequence has been an explosion of interest in two-phase intermetallic-based alloys.With the exception of some early work by Seybolt, intermetallic matrices have been utilized for composites only for the past five to six years; the first published reference to systematic studies of fibrous composites dates from the proceedings of an MRS meeting in December 1986. The published literature is much sparser than, for example, that on ceramic matrix composites, which have been under development for a much longer period. Nevertheless, an appreciable number of intermetallic matrices have been reinforced with fibers or particles.Because of the relatively high melting points and extreme brittleness of most intermetallic compounds utilized as matrices, as well as other significant advantages, enormous effort has been devoted to powder metallurgical techniques. In this category we include reactive sintering of elemental or elemental plus prealloyed powders, reactive hot pressing, reactive HIPing, injection molding, the XD process, dynamic compaction of powders, mechanical alloying, the powder cloth method, and, of course, traditional hot pressing techniques.

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

MRS Proceedings ◽

10.1557/proc-350-279 ◽

1994 ◽

Vol 350 ◽

Author(s):

François-charles dary ◽

Shiela R. Woodard ◽

Tresa M. Pollock

Keyword(s):

High Temperature ◽

Titanium Aluminides ◽

Matrix Composites ◽

Low Oxygen ◽

Microstructural Stability ◽

Two Phase ◽

Intermetallic Matrix ◽

Three Phase ◽

Temperature Exposure

AbstractA 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.

The effect of reinforcement size on the creep strength of intermetallic matrix composites

Materials Science and Engineering A ◽

10.1016/0921-5093(92)90234-r ◽

1992 ◽

Vol 153 (1-2) ◽

pp. 438-443 ◽

Cited By ~ 19

Author(s):

J Rösler ◽

A.G Evans

Keyword(s):

Creep Strength ◽

Matrix Composites ◽

Intermetallic Matrix ◽

The Formation Process of the Microstructure of Al2O3-Al3Ti-Al In-Situ Composite

Microscopy and Microanalysis ◽

10.1017/s1431927600010527 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 727-728

Author(s):

H.H. Luo ◽

D.Z. Wang ◽

H.X. Peng ◽

Cheng Liu ◽

C.K. Yao

Keyword(s):

Squeeze Casting ◽

Volume Fraction ◽

Average Diameter ◽

Matrix Composites ◽

Intermetallic Matrix ◽

Al Composite ◽

Heat Treated ◽

Processing Techniques

In the last decade, new in-situ processing techniques, such as DIMOX™, XD™, VLS and SHS, for fabricating metal and intermetallic matrix composites have emerged. It is expected that the in-situ formed composites may reveal not only excellent dispersion of fine reinforcing particles, but high thermodynamical stability and high temperature performance. The fully dense Al2O3-Al3Ti-57Vol%Al composite was in-situ processed by combing combustion synthesis with squeeze casting utilizing the reaction between TiO2 powder (with average diameter of 0.6μm and volume fraction of 14%) and pure Al (99.5%). First, the 14Vol%TiO2/Al bulk materials were fabricated via squeeze casting method, subsequently, the TiO2/Al materials were heat treated to form final in-situ composites. Using XRD, SEM, TEM and HRTEM techniques, the microstructure and its evolution were investigated.The X-ray diffraction pattern of the composite is shown in Fig.1 which indicates that the composite is composed of A12O3, Al3Ti and Al. According to the reaction formula between TiO2 and Al the volume fraction of Al in the composite is about 57%. Fig.2 is a typical scanning electron micrograph of the composite.

The effect of reinforcement size on the creep strength of intermetallic matrix composites

High Temperature Aluminides and Intermetallics ◽

10.1016/b978-1-85166-822-9.50071-6 ◽

1992 ◽

pp. 438-443 ◽

Cited By ~ 1

Author(s):

J. Rösler ◽

A.G. Evans

Keyword(s):

Creep Strength ◽

Matrix Composites ◽

Intermetallic Matrix ◽

Microstructural characterization of plasma-processed Ti-Al metal matrix composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154731 ◽

1989 ◽

Vol 47 ◽

pp. 552-553

Author(s):

M. G. Burke ◽

M. N. Gungor ◽

M. A. Burke

Keyword(s):

High Temperature ◽

Titanium Aluminide ◽

Plasma Processing ◽

Microstructural Characterization ◽

High Temperature Strength ◽

Matrix Composites ◽

Intermetallic Matrix ◽

Long Time ◽

Strength And Stiffness ◽

Intermetallic matrix composites are candidates for ultrahigh temperature service when light weight and high temperature strength and stiffness are required. Recent efforts to produce intermetallic matrix composites have focused on the titanium aluminide (TiAl) system with various ceramic reinforcements. In order to optimize the composition and processing of these composites it is necessary to evaluate the range of structures that can be produced in these materials and to identify the characteristics of the optimum structures. Normally, TiAl materials are difficult to process and, thus, examination of a suitable range of structures would not be feasible. However, plasma processing offers a novel method for producing composites from difficult to process component materials. By melting one or more of the component materials in a plasma and controlling deposition onto a cooled substrate, a range of structures can be produced and the method is highly suited to examining experimental composite systems. Moreover, because plasma processing involves rapid melting and very rapid cooling can be induced in the deposited composite, it is expected that processing method can avoid some of the problems, such as interfacial degradation, that are associated with the relatively long time, high temperature exposures that are induced by conventional processing methods.