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 of Ni–Ni3Si eutectic in situ composites by electron beam floating zone melting

2013 ◽  
Vol 412 ◽  
pp. 70-73 ◽  
Author(s):  
Chunjuan Cui ◽  
Jun Zhang ◽  
Kun Wu ◽  
Dening Zou ◽  
Youping Ma ◽  
...  
Keyword(s):  
Electron Beam ◽  
Directional Solidification ◽  
Zone Melting ◽  
Floating Zone ◽  
In Situ Composites

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.

Tensile and Fracture Behavior of NbSS/Nb5Si3 In Situ Composites Prepared by Arc Melting

2005 ◽  
Vol 297-300 ◽  
pp. 507-514
Author(s):  
Jin Hak Kim ◽  
Tatsuo Tabaru ◽  
Michiru Sakamoto ◽  
Shuji Hanada
Keyword(s):  
Base Composition ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Secondary Phase ◽  
Secondary Phases ◽  
In Situ Composites ◽  
Arc Melting ◽  
Negative Effect ◽  
Base Composite

Nb-base in-situ composites, which have the base composition of Nb-18Si-5Mo-5Hf, have been investigated in microstructure, hardness (Hv*), Young’s modulus (E), tensile properties and fracture behavior. The microstructures of all composites examined consist of NbSS matrix and Nb5Si3 secondary phases. No secondary phase such as Nb2C appeared. The crystal structure of Nb5Si3 is Mn5Si3-type when C replaces 2mol%-Nb, though typical structures of a (Cr5B3-type) and b (W5Si3-type) as in the base composition when W replaces. W addition is effective in increasing Hv* and E of both phases as expected. However, C alloying is somewhat beneficial only in Nb5Si3 with a noticeable negative effect in NbSS. Furthermore, the composite exhibits the highest strength at 1473 K, while the base composite exhibits the highest at room temperature. The fracture behavior is independent of the compositions and it is controlled by cleavage fractures of Nb5Si3, decohesion of NbSS/Nb5Si3 interface and ductile rupture of NbSS depending on the testing temperatures.

Microstructure and Mechanical Properties of an Advanced Niobium Based Ultrahigh Temperature Alloy

2007 ◽  
Vol 539-543 ◽  
pp. 3690-3695 ◽  
Author(s):  
X.P. Guo ◽  
L.M. Gao ◽  
Ping Guan ◽  
K. Kusabiraki ◽  
Heng Zhi Fu
Keyword(s):  
Mechanical Properties ◽  
Electron Beam ◽  
Directional Solidification ◽  
Room Temperature ◽  
Zone Melting ◽  
Floating Zone ◽  
Directionally Solidified ◽  
Microstructure And Mechanical Properties ◽  
Temperature Fracture ◽  
Ultrahigh Temperature

The microstructure and mechanical properties including room temperature fracture toughness Kq, tensile strengthσb and elongationδ at 1250°C of the Nb based alloy directionally solidified in an electron beam floating zone melting (EBFZM) furnace have been evaluated. The microstructure is primarily composed of Nb solid solution (Nbss), α-(Nb)5Si3 and (Nb)3Si phases. After directional solidification with the moving rate of electron beam gun R being respectively 2.4, 4.8 and 7.2 mm/min, the primary Nbss dendrites, Nbss + (Nb)5Si3/(Nb)3Si eutectic colonies (lamellar or rod-like) and divorced Nb silicide plates align along the longitudinal axes of the specimens. When R = 2.4 mm/min, the best directional microstructure is obtained. Directional solidification has significantly improved theσb at 1250°C and Kq. The maximumσb occurs for the specimens with R = 2.4 mm/min and is about 85.0 MPa, meanwhile, the Kq is about 19.4 MPam1/2.

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