Mechanical Behavior of MoSi₂ Reinforced–Si₃N₄Matrix Composites

Abstract

The mechanical behavior of MoSi2 reinforced–Si3N4 matrix composites was investigated as a function of MoSi2 phase content, MoSi2 phase size, and amount of MgO densification aid for the Si3N4 phase. Coarse‐phase MoSi2‐Si3N4 composites exhibited higher room‐temperature fracture toughness than fine‐phase composites, reaching values >8 MP·am1/2. Composite fracture toughness levels increased at elevated temperature. Fine‐phase composites were stronger and more creep resistant than coarse phase composites. Room‐temperature strengths >1000 MPa and impression creep rates of ∼10−8 s−1 at 1200°C were observed. Increased MgO levels generally were deleterious to MoSi2‐Si3N4 mechanical properties. Internal stresses due to MoSi2 and Si3N4 thermal expansion coefficient mismatch appeared to contribute to fracture toughening in MoSi2‐Si3N4 composites.

MoSi2–Si3N4 composites: Influence of starting materials and fabrication route on electrical and mechanical properties

“…5 Coarse-phase MoSi 2 -Si 3 N 4 composites exhibited higher room temperature fracture toughness than fine-phase composites, reaching values >8 MPa m 1/2 . On the other hand, the inclusion of a certain amount of electroconductive MoSi 2 particles into the insulating Si 3 N 4 matrix, similar to the inclusion of TiN particles, 18 can lead to electrically conductive composites and this can facilitate their machining into complex shapes by the economical electrical discharge machining (EDM) technique.…”

“…The need for improving fracture toughness, high temperature and electrical properties, and machinability of Si 3 N 4 -based materials has led to the recent development of MoSi 2 -particle reinforced-Si 3 N 4 composites. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The combination of Si 3 N 4 and MoSi 2 gives MoSi 2 -Si 3 N 4 composite materials with desirable mechanical properties and good electrical conductivity. The intermetallic compound MoSi 2 has long been known as a high temperature material that has excellent oxidation resistance and electrical conductivity (2 × 10 5 −1 cm −1 at room temperature).…”

The effect of different sintering additives on the electrical and oxidation properties of Si3N4–MoSi2 composites

“…conductive composites, this can facilitate machining of these composites into complex shapes by the more economical electrical discharge machining (EDM). 4 Various Si 3 N 4 composites with addition of an electroconductive secondary phase, such as TiN, 3 TiB 2 , 5 TaN, 6,7 TiC 8 and MoSi 2 , 9,10 have been studied. Among them, Si 3 N 4 -MoSi 2 composites are of special interest.…”

High‐Strength and ‐Toughness Electroconductive SiC‐Based Composites

“…In this work, MoSi 2 was selected as the secondary electroconductive phase for a silicon carbide matrix, as MoSi 2 has a low electrical resistivity as well as a series of interesting properties, such as the high melting point, high thermal conductivity and excellent oxidation resistance. [8] MoSi 2 has been coupled to several ceramic matrixes, such as Si 3 N 4 , SiC, SiAlON, AlN and it has been found that its addition causes a significant improvement in the mechanical properties [9][10][11][12][13][14] and the oxidation resistance. [15][16] In this contribution, the microstructure and properties of SiC-based composites containing 10 and 30 vol% of MoSi 2 particulate are presented and compared to those of the reference SiC and MoSi 2 monolithic materials.…”

“…In the reinforced composite containing 30 vol% of MoSi 2 , the fracture toughness increased of about 27 % in comparison with the reference SiC material. Similar to other MoSi 2 -reinforced materials, [9][10][11][12] one of the toughening mechanisms which were likely to occur in these composites is the residual stresses mechanism, [23] due to the difference in thermal expansion coefficient (CTE) between the reinforcing particles (9.1·10 -6 /°C for MoSi 2 [21] ) and the SiC matrix (5.1·10 -6 /°C [21] ). According to the theoretical model of Taya at al.…”