Preparation of Ti-Al Intermetallics by Aluminum Melt Infiltration-Diffusion Annealing Technique

2007 ◽  
Vol 561-565 ◽  
pp. 367-370
Author(s):  
Li Qing Chen ◽  
Ji Jie Wang ◽  
Lin Chen
Keyword(s):  
High Temperature ◽  
Reaction Mechanism ◽  
Melting Point ◽  
Elevated Temperatures ◽  
Diffusion Annealing ◽  
Compressive Behavior ◽  
Porous Ti ◽  
Temperature Diffusion ◽  
Melt Infiltration ◽  
Long Time

A novel process, of melt infiltration combined with diffusion annealing technique, was developed to prepare Ti-Al intermetallics at temperature lower than ingot melting point. In this process, a porous Ti preform was firstly fabricated and the Al melt was reheated to temperature slightly higher than Al melting point to infiltrate the porous Ti preform by capillary force spontaneously. After long-time high-temperature diffusion annealing, Ti-Al intermetallic compound can be finally synthesized from the bulk Tip+melt Al via diffusion. As example, Ti-46Al intermetallics has been fabricated, and the microstructures and the phases of the as-synthesized intermetallics were characterized by XRD and SEM. The compressive behavior of the as-synthesized Ti-Al at elevated temperatures has been studied and the reaction mechanism involved in the process finally analyzed.

Synthesis of High-Temperature Silicides Via Rapid Solid-State Metathesis

1993 ◽  
Vol 322 ◽  
Author(s):  
Richard M. Jacubinas ◽  
Richard B. Kaner
Keyword(s):  
High Temperature ◽  
Solid State ◽  
Melting Point ◽  
Alkaline Earth ◽  
Elevated Temperatures ◽  
High Strength ◽  
Heat Of Formation ◽  
High Melting Point ◽  
Temperature Oxidation ◽  
Oxidation And Corrosion

AbstractMosi2 has a very favorable combination of materials properties, including a high melting point (2020°C), high strength at elevated temperatures, and resistance to high temperature oxidation and corrosion. These properties make it a good candidate for a hightemperature structural material; however, it has very poor ductility. A great deal of research has focused on improving the ductility of this alloy through various preparative routes. We have synthesized Mosi2, as well as WSi2, TaSi2, and NbSi2, using rapid solid-state metathesis reactions between a high oxidation state metal halide and an alkaline earth silicide. These reactions take advantage of the large exothermic heat of formation of the alkaline earth halide and can reach temperatures as high as the melting point of the product silicides. In addition, this approach yields crystalline products in seconds. The synthetic technique will be discussed along with characterization results.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

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

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

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.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

High temperature compressive behavior of three-dimensional five-directional braided composites

2018 ◽  
Vol 60 (7-8) ◽  
pp. 772-776 ◽  
Author(s):  
Jiayi Liu ◽  
Junmeng Zhou ◽  
Yu Wang ◽  
Jie Mei ◽  
Jialin Liu
Keyword(s):  
High Temperature ◽  
Three Dimensional ◽  
Compressive Behavior ◽  
Braided Composites

WIELAND-K88

Alloy Digest ◽  
2005 ◽  
Vol 54 (12) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Stress Relaxation ◽  
Copper Alloy ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
Relaxation Resistance ◽  
Temperature Performance ◽  
Very High

Abstract Wieland K-88 is a copper alloy with very high electrical and thermal conductivity, good strength, and excellent stress relaxation resistance at elevated temperatures. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: CU-738. Producer or source: Wieland Metals Inc.

UNS N06455

Alloy Digest ◽  
1989 ◽  
Vol 38 (1) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Stress Corrosion Cracking ◽  
Temperature Stability ◽  
Heat Treating ◽  
High Ductility ◽  
High Temperature Stability ◽  
Nickel Chromium ◽  
Long Time ◽  
Resistance To Stress

Abstract UNS NO6455 is a nickel-chromium-molybdenum alloy with outstanding high-temperature stability as shown by high ductility and corrosion resistance even after long-time aging in the range 1200-1900 F. The alloy also has excellent resistance to stress-corrosion cracking and to oxidizing atmospheres up to 1900 F. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-367. Producer or source: Nickel and nickel alloy producers.

DOWMETAL HZ32XA

Alloy Digest ◽  
1956 ◽  
Vol 5 (7) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Creep Resistance ◽  
Zirconium Alloy ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
High Temperature Creep ◽  
Aged Condition ◽  
Chemical Company ◽  
Temperature Performance

Abstract DOWMETAL HZ32XA is a magnesium-thorium-zinc-zirconium alloy having good high temperature creep resistance, and is recommended for applications at elevated temperatures. It is used in the artificially aged condition (T5). This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance as well as heat treating, machining, and joining. Filing Code: Mg-26. Producer or source: The Dow Chemical Company.

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