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

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.

Download Full-text

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

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.261-263.1439 ◽

2004 ◽

Vol 261-263 ◽

pp. 1439-1444 ◽

Cited By ~ 3

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.

Download Full-text

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

Key Engineering Materials - Advances in Fracture and Strength ◽

10.4028/0-87849-978-4.507 ◽

2005 ◽

pp. 507-514

Author(s):

Jin Hak Kim ◽

Tatsuo Tabaru ◽

Michiru Sakamoto ◽

Shuji Hanada

Keyword(s):

Fracture Behavior ◽

In Situ Composites ◽

Arc Melting

Download Full-text

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

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.306-308.941 ◽

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.

Download Full-text

Controlling microstructural evolution to in situ toughen and strengthen silicon carbide

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165926 ◽

1996 ◽

Vol 54 ◽

pp. 692-693 ◽

Cited By ~ 1

Author(s):

Warren J. MoberlyChan ◽

J. J. Cao ◽

L. C. DeJonghe

Keyword(s):

Crack Propagation ◽

Room Temperature ◽

Grain Shape ◽

Secondary Phase ◽

Fracture Path ◽

Secondary Phases ◽

Structural Applications ◽

Temperature Fracture ◽

Nonoxide Ceramics

Nonoxide ceramics are desirable for high temperature structural applications, however, they have typically exhibited inferior room temperature fracture toughness. Similar to processing developments to toughen Si3N4, SiC has recently been processed via control of a phase transformation to produce in situ toughened microstructures. An elongated grain shape, coupled with a tortuous fracture path around grains, can provide bridging behind an advancing crack tip, which increases the crack resistance (rising R curve) and halts crack propagation. Most in situ toughened nonoxide ceramics incorporate upwards of 10-20% secondary phase(s), which simplifies crack propagation through this weaker phase to improve toughness, but typically at the expense of substantially reducing strength at high temperatures. The ABC-SiC in this study can be processed with <3% secondary phases and consequently exhibits record toughness and higher strength than commercial (Hexoloy SA) SiC.

Download Full-text

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

MRS Proceedings ◽

10.1557/opl.2012.1564 ◽

2012 ◽

Vol 1516 ◽

pp. 255-260 ◽

Cited By ~ 2

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.

Download Full-text

In situ nuclear-glass corrosion under geological repository conditions

npj Materials Degradation ◽

10.1038/s41529-019-0100-7 ◽

2019 ◽

Vol 3 (1) ◽

Cited By ~ 3

Author(s):

Mathieu Debure ◽

Yannick Linard ◽

Christelle Martin ◽

Francis Claret

Keyword(s):

Pure Water ◽

Secondary Phase ◽

Predictive Modelling ◽

Diffusion Experiment ◽

Secondary Phases ◽

Glass Corrosion ◽

Geological Repository ◽

High Level ◽

Rock Supports

Abstract Silicate glasses are durable materials but laboratory experiments reveal that elements that derive from their environment may induce high corrosion rates and reduce their capacity to confine high-level radioactive waste. This study investigates nuclear-glass corrosion in geological media using an in situ diffusion experiment and multi-component diffusion modelling. The model highlights that the pH imposed by the Callovo–Oxfordian (COx) claystone host rock supports secondary-phase precipitation and increases glass corrosion compared with pure water. Elements from the COx rock (mainly Mg and Fe) form secondary phases with Si provided by the glass, which delay the establishment of a passivating interface. The presence of elements (Mg and Fe) that sustain glass alteration does not prevent a significant decrease in the glass-alteration rate, mainly due to the limited species transport that drives system reactivity. These improvements in the understanding of glass corrosion in its environment provide further insights for predictive modelling over larger timescales and space.

Download Full-text