Effect of carbon on microstructure and high-temperature strength of NbMoTiSi in situ composites prepared by arc-melting and directional solidification

2003 ◽  
Vol 343 (1-2) ◽  
pp. 282-289 ◽  
Author(s):  
Jiangbo Sha ◽  
Hisatoshi Hirai ◽  
Tatsuo Tabaru ◽  
Akira Kitahara ◽  
Hidetoshi Ueno ◽  
...  
Keyword(s):  
High Temperature ◽  
Directional Solidification ◽  
High Temperature Strength ◽  
In Situ Composites ◽  
Arc Melting

Effect of HfC Addition on Mechanical Properties of Nb-5Mo-2W-18Si In-Situ Composites

2004 ◽  
Vol 261-263 ◽  
pp. 1439-1444 ◽  
Author(s):  
Sheng Wu Wang ◽  
Hisatoshi Hirai ◽  
Tatsuo Tabaru ◽  
A. Kitahara ◽  
Hideto Ueno
Keyword(s):  
Mechanical Properties ◽  
Directional Solidification ◽  
Base Composition ◽  
Zone Melting ◽  
Shearing Stress ◽  
Floating Zone ◽  
In Situ Composites ◽  
Arc Melting ◽  
Microcrack Propagation

Nb base in-situ composites with the base composition of Nb-5Mo-2W-18Si were prepared by conventional arc-melting and induction heating floating zone melting followed by directional solidification. To investigate the effect of HfC addition, Nb was replaced with 0, 1 and 2 mol% HfC. The in-situ composites predominantly have an eutectic microstructure consisting of Nb solid solution (NbSS) and (Nb,Mo,W))5Si3 (5-3 silicide). The strength at 1470 K and 1670 K increases without fracture toughness decreasing, with increasing the HfC content. Directional solidification also improves the strength at the high temperature. The slip band under the shearing stress occurs in the NbSS during plastic deformation, which contributes to suppress microcrack propagation. It seems that HfC addition reinforces the bonding strength at grain boundary or NbSS/5-3 silicide interface.

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.

Mechanical properties of NiAl-Mo composites produced by specially controlled directional solidification

2012 ◽  
Vol 1516 ◽  
pp. 255-260 ◽  
Author(s):  
G. Zhang ◽  
L. Hu ◽  
W. Hu ◽  
G. Gottstein ◽  
S. Bogner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Directional Solidification ◽  
Creep Resistance ◽  
Room Temperature ◽  
Growth Direction ◽  
Nominal Composition ◽  
Potential Candidate ◽  
In Situ Composites

ABSTRACTMo fiber reinforced NiAl in-situ composites with a nominal composition Ni-43.8Al-9.5Mo (at.%) were produced by specially controlled directional solidification (DS) using a laboratory-scale Bridgman furnace equipped with a liquid metal cooling (LMC) device. In these composites, single crystalline Mo fibers were precipitated out through eutectic reaction and aligned parallel to the growth direction of the ingot. Mechanical properties, i.e. the creep resistance at high temperatures (HT, between 900 °C and 1200 °C) and the fracture toughness at room temperature (RT) of in-situ NiAl-Mo composites, were characterized by tensile creep (along the growth direction) and flexure (four-point bending, vertical to the growth direction) tests, respectively. In the current study, a steady creep rate of 10-6s-1 at 1100 °C under an initial applied tensile stress of 150MPa was measured. The flexure tests sustained a fracture toughness of 14.5 MPa·m1/2at room temperature. Compared to binary NiAl and other NiAl alloys, these properties showed a remarkably improvement in creep resistance at HT and fracture toughness at RT that makes this composite a potential candidate material for structural application at the temperatures above 1000 °C. The mechanisms responsible for the improvement of the mechanical properties in NiAl-Mo in-situ composites were discussed based on the investigation results.

Processing high-temperature refractory-metal silicide in-situ composites

JOM ◽  
1999 ◽  
Vol 51 (4) ◽  
pp. 32-36 ◽  
Author(s):  
B. P. Bewlay ◽  
M. R. Jackson ◽  
P. R. Subramanian
Keyword(s):  
High Temperature ◽  
Refractory Metal ◽  
Metal Silicide ◽  
In Situ Composites

scholarly journals Nanoscaled eutectic NiAl-(Cr,Mo) composites with exceptional mechanical properties processed by electron beam melting

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Andreas Förner ◽  
S. Giese ◽  
C. Arnold ◽  
P. Felfer ◽  
C. Körner ◽  
...  
Keyword(s):  
Electron Beam ◽  
High Temperature ◽  
Electron Beam Melting ◽  
Lamellar Microstructure ◽  
High Hardness ◽  
Additive Process ◽  
In Situ Composites ◽  
Selective Electron Beam Melting ◽  
Very High

Abstract Eutectic NiAl-(Cr,Mo) composites are promising high temperature materials due to their high melting point, excellent oxidation behavior and low density. To enhance the strength, hardness and fracture toughness, high cooling rates are beneficial to obtain a fine cellular-lamellar microstructure. This can be provided by the additive process of selective electron beam melting. The very high temperature gradient achieved in this process leads to the formation of the finest microstructure that has ever been reported for NiAl-(Cr,Mo) in-situ composites. A very high hardness and fracture toughening mechanisms were observed. This represents a feasibility study towards additive manufacturing of eutectic NiAl-(Cr,Mo) in-situ composites by selective electron beam melting.

Microstructures and High-temperature Strength of Silicide-reinforced Nb Alloys

2000 ◽  
Vol 646 ◽  
Author(s):  
C.L. Ma ◽  
Y. Tan ◽  
H. Tanaka ◽  
A. Kasama ◽  
R. Tanaka ◽  
...  
Keyword(s):  
High Temperature ◽  
Quaternary System ◽  
Eutectic Reaction ◽  
High Temperature Strength ◽  
Quaternary Alloys ◽  
Two Phase ◽  
Practical Applications ◽  
Arc Melting ◽  
Heat Treated ◽  
Very High

ABSTRACTThis article describes the phase stability, microstructures and mechanical properties of silicide-reinforced Nb alloys in Nb-Mo-W-Si quaternary system prepared by arc melting and heat treatment. There exists an equilibrium two-phase field of Nb solid solution (Nbss) and α(Nb,Mo,W)5Si3 in a Nb-rich region of this quaternary system. Alloys in this region have a eutectic reaction of L → Nbss+β(Nb,Mo,W)5Si3 during solidification. The β(Nb,Mo,W)5Si3 transforms to the stable α(Nb,Mo,W)5Si3 at very high temperature. The cast and heat treated hypoeutectic alloys consist of dendritic Nbss, network-shaped Nbss matrix and α(Nb,Mo,W)5Si3. These quaternary alloys exhibit excellent high-temperature strength, although the fracture toughness is still unacceptable for practical applications.

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