Ti-Modified Niobium-Silicide Based Directionally Solidified in-situ Composites

1996 ◽  
Vol 460 ◽  
Author(s):  
B. P. Bewlay ◽  
M. R. Jackson ◽  
H. A. Lipsitt
Keyword(s):  
Solid Solution ◽  
Fracture Toughness ◽  
High Temperature ◽  
Cold Crucible ◽  
Directionally Solidified ◽  
In Situ Composites ◽  
Czochralski Crystal Growth ◽  
Three Phase ◽  
Binary Eutectic

ABSTRACTThis paper examines microstructure-property relationships in high-temperature directionally solidified (DS) in-situ composites based on Nb silicides, such as Nb3Si and Nb5Si3. These in-situ composites are based on the Nb3Si-Nb binary eutectic, and are alloyed with Ti. They were prepared using cold crucible Czochralski crystal growth. Ternary Nb-Ti-Si alloys with Ti concentrations from 9 to 45%, and Si concentrations from 10 to 25%, were directionally solidified to generate aligned two- and three-phase composites containing a Nb solid solution with Nb3Si and Nb5Si3 silicides. Fracture toughness values generally greater than 10 MPa√m were measured in these composites. For a given Si concentration, the fracture toughness of the Ti-containing composites was increased ∼ 6 MPa√m over that of the binary alloy composites. The effects of Si concentration, and a range of Nb:Ti ratios, on microstructure, phase equilibria, and fracture toughness were examined.

Microstructures and Properties of Ds in-Situ Composites of Nb-Ti-Si Alloys

1994 ◽  
Vol 364 ◽  
Author(s):  
B. P. Bewlay ◽  
M. R. Jackson ◽  
W. J. Reeder ◽  
H. A. Lipsitt
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Fracture Toughness ◽  
Room Temperature ◽  
In Situ Composites ◽  
Environmental Resistance ◽  
High Temperature Mechanical Properties ◽  
Three Phase ◽  
Temperature Fracture

AbstractIn-situ composites based on binary Nb-Si alloys and consisting of a Nb solid solution with Nb3Si or Nb5Si3 have shown a promising combination of low temperature and high temperature mechanical properties. The environmental resistance and room temperature fracture toughness of these composites can be further enhanced by additions such as Ti, Hf, Cr, and Al. In the present study, ternary Nb-Ti-Si alloys were prepared by directional solidification to generate aligned two and three phase composites containing a Nb solid solution with Nb3Si and/or Nb5Si3. The present paper will describe microstructures, phase equilibria and fracture toughness of these composites. The improvement in the room temperature fracture toughness over binary Nb-Nb5Si3 composites is discussed.

Microstructural Response of DS Nb-Silicide In-Situ Composites During High-Temperature Creep Testing

2000 ◽  
Vol 6 (S2) ◽  
pp. 376-377
Author(s):  
B.P. Bewlay ◽  
S.D. Sitzman
Keyword(s):  
High Temperature ◽  
Electron Backscatter Diffraction ◽  
Czochralski Method ◽  
Longitudinal Section ◽  
Creep Testing ◽  
Directionally Solidified ◽  
Creep Tests ◽  
In Situ Composites ◽  
Structural Applications

Directionally solidified (DS) in-situ composites based on (Nb) and Nb silicides, such as Nb5Si3 and Nb3Si, are being investigated for high-temperature structural applications. The use of alloying additions, such as Hf, Ti and Mo, to these silicides is required to enhance their properties. The present paper describes the microstructural response of a DS Nb-silicide based composite to creep testing.The composites investigated were directionally solidified from a molten alloy using the Czochralski method as described previously. Creep tests were conducted at 1200°C to strains of up 50%. Microstructure and microtexture characterizations were performed using scanning electron microscopy, electron microprobe analysis (EMPA), and electron backscatter diffraction pattern analysis (EBSP).Microstructures of the longitudinal section of a DS composite generated from a Nb-12.5Hf-33Ti- 16Si alloy are shown in Figure 1 in the as-DS (left hand side) and the DS+creep tested conditions (right hand side).

Directional Solidification and Characterization of Al2O3/Er3Al5O12 Eutectic In Situ Composite by Laser Zone Remelting

2010 ◽  
Vol 654-656 ◽  
pp. 1347-1350 ◽  
Author(s):  
Hai Jun Su ◽  
Jun Zhang ◽  
Yang Fang Deng ◽  
Kan Song ◽  
Lin Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Directional Solidification ◽  
Laser Scanning ◽  
Growth Characteristic ◽  
High Rate ◽  
Full Density ◽  
In Situ Composites ◽  
Selective Emitter ◽  
Binary Eutectic

Directionally solidified (DS) oxide eutectic in situ composites are attracting increasing attention because of their unique properties and potential applications to high temperature structural materials, optical or electronic devices. Among the alumina-based eutectic composites, DS Al2O3/Er3Al5O12(EAG) eutectic is considered to be promising candidate for use as selective emitter at high temperature. In this work, eutectic in situ composites of Al2O3/EAG rods having smooth surface and full density are successfully prepared by directional solidification using the laser zone remelting method, aiming to investigate the growth characteristic of this novel binary eutectic under high temperature gradient. The microstructure is investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). The Al2O3/EAG eutectic presents a very fine irregular network structure consisting of only -Al2O3 and Er3Al5O12 phases without grain boundaries and amorphous phases between interfaces. The eutectic interphase spacing is strongly dependent on the laser scanning rate, rapidly decreasing at the sub-micron levels for the samples grown at high rate. Furthermore, the microstructural formation and evolution of the composite are analyzed and discussed.

Effects of Re Alloying on Mechanical Properties of In-Situ Composites with Base Composition of Nb-18Si-2HfC

2006 ◽  
Vol 306-308 ◽  
pp. 941-946
Author(s):  
Sheng Wu Wang ◽  
Tatsuo Tabaru ◽  
Hisatoshi Hirai ◽  
Hideto Ueno
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Temperature ◽  
Base Composition ◽  
Room Temperature ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
In Situ Composites ◽  
Temperature Fracture

Nb-base in-situ composites with the base composition of Nb-18Si-2HfC were prepared by conventional arc-melting. Their microstructures and mechanical properties, such as high-temperature strength and room temperature fracture toughness, were investigated to elucidate the effects of Re alloying. The in-situ composites predominantly have eutectic microstructures consisting of an Nb solid solution (NbSS) and Nb5Si3. The compressive strength increased with the increasing Re contents at 1470K and not at 1670 K. The strengthening effect observed at 1470 K is higher than that by W and Mo. Re alloying of about 2 % is valuable for improving both the high temperature strength and room temperature fracture toughness of Nb-18Si-2HfC base materials.

The microstructure and crystallography of the Cr-Cr3Si eutectic

1991 ◽  
Vol 49 ◽  
pp. 598-599
Author(s):  
J.A. Sutlif ◽  
B.P. Bewlay ◽  
K.M. Chang ◽  
M.R. Jackson
Keyword(s):  
High Temperature ◽  
High Strength ◽  
Aircraft Engine ◽  
Microstructural Stability ◽  
Directionally Solidified ◽  
In Situ Composites ◽  
Interface Reactions ◽  
Engine Components ◽  
Directionally Solidified Eutectics

New materials for high temperature aircraft engine components should have a good combination of low density and high strength at temperatures as high as 1300-1500°C. This will probably require the use of composite materials. In-situ composites, or directionally solidified eutectics, are good candidates for this demanding application and have major advantages over alternative synthetic composites, such as MoSi2-SiC or carbon-carbon composites. The fabrication of components from eutectic castings is simpler and eutectic alloys offer some intrinsic microstructural stability with no reinforcement-matrix interface reactions at high temperatures. We are investigating the Cr-Si, Nb-Si and V-Si eutectic systems as potential high temperature in-situ composites. In this paper, we present results on the microstructure and crystallography of the Cr-Cr3Si eutectic which has a eutectic composition of ∼15 at% Si and a melting temperature of ∼1705 °C.

Microstructure and room temperature fracture toughness of directionally solidified NiAl–Mo eutectic in situ composites

2012 ◽  
Vol 21 (1) ◽  
pp. 18-25 ◽  
Author(s):  
Jian-Fei Zhang ◽  
Jun Shen ◽  
Zhao Shang ◽  
Zhou-Rong Feng ◽  
Ling-Shui Wang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Room Temperature ◽  
Directionally Solidified ◽  
In Situ Composites ◽  
Temperature Fracture

ALTEMP HX

Alloy Digest ◽  
1993 ◽  
Vol 42 (10) ◽  
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Base Alloy ◽  
Heat Treating ◽  
Nickel Base Alloy ◽  
Temperature Performance ◽  
Nickel Base

Abstract ALTEMP HX is an austenitic nickel-base alloy designed for outstanding oxidation and strength at high temperatures. The alloy is solid-solution strengthened. Applications include uses in the aerospace, heat treatment and petrochemical markets. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, and joining. Filing Code: Ni-442. Producer or source: Allegheny Ludlum Corporation.

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