Mechanical behavior and interface design of MoSi2-based alloys and composites (original) (raw)
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MICROSTRUCTURE AND MECHANICAL PROPERTIES OF MoSi2 - BASES COMPOSITES
2005
The purpose of the present investigation was to explore microstructure and mechanical properties of composite materials with different amounts of secondary phase (SiC, nano SiC, Si3N4), and their comparison with monolithic MoSi2. The main criteria for the assessment of mechanical properties were hardness, mechanical strength, and fracture toughness determined by two different methods. The results showed that composite materials with 10% nano SiC particles had the best mechanical properties compared to all other studied materials. The creep resistance of MoSi2 composite materials in ambient atmosphere was studied in the temperature range 1000 – 1400°C under a load of 100 MPa.
Alloying of MoSi 2 for improved mechanical properties
Intermetallics, 2001
Effects of alloying on mechanical properties of solidification processed polycrystalline MoSi 2 , ternary (Mo, 2.5 at.% Re)Si 2 , Mo(2 at.% Al, Si) 2 , (Mo, 1 at.% Nb)Si 2 , and quaternary (Mo, 1 at.% Re)( 2 at.% Al, Si) 2 alloys were evaluated by microhardness testing at room temperature and compression testing at elevated temperatures. Alloying with 2.5 at.% Re resulted in an anomalously high solid solution hardening in MoSi 2 , while alloying with 2 at.% Al lowered the brittle-to-ductile transition temperature, in compression, of polycrystalline MoSi 2 from 900 o C to 425 o C. Similar to the effects observed in the quaternary (Mo, 1 at.% Re)(2 at.% Al, Si) 2 alloy, 1 at.% Nb containing samples exhibited concurrent enhanced ambient temperature ductility and higher elevated temperature strength compared to pure MoSi 2 . The effects of alloying MoSi 2 with 2.5 at.% Re, 1 at.% Re+2 at.% Al, and 1 at.% Nb on hardness and yield strength are discussed. #
Processing, microstructure, properties, and applications of MoSi2-containing composites: a review
Frontiers in Materials
Intermetallic molybdenum disilicide (MoSi2) possesses unique physical, chemical, thermal, and mechanical properties that make it compatible with some ceramics (SiC, Al2O3) and metals (Cu, Al) to manufacture composite materials. Its current applications, chiefly limited to heating elements, can be expanded if its properties are judiciously combined with those of other materials like SiC or Al to produce ceramic- and metal-matrix composites with improved mechanical, thermal, functional, or even multifunctional properties. This review presents a perspective on the feasibility of manufacturing ceramic- and metallic-based MoSi2 composite materials. A comprehensive discussion of the pros and cons of current liquid-state and solid-state processing routes for MoSi2 metal-matrix composites and the resulting typical microstructures is presented. Although MoSi2 has been studied for more than five decades, it was not until recently that industrial applications demanding high temperature and cor...
Frontiers in Materials, 2023
Intermetallic molybdenum disilicide (MoSi2) possesses unique physical, chemical, thermal, and mechanical properties that make it compatible with some ceramics (SiC, Al2O3) and metals (Cu, Al) to manufacture composite materials. Its current applications, chiefly limited to heating elements, can be expanded if its properties are judiciously combined with those of other materials like SiC or Al to produce ceramic- and metal-matrix composites with improved mechanical, thermal, functional, or even multifunctional properties. This review presents a perspective on the feasibility of manufacturing ceramic- and metallic-based MoSi2 composite materials. A comprehensive discussion of the pros and cons of current liquid-state and solid-state processing routes for MoSi2 metal-matrix composites and the resulting typical microstructures is presented. Although MoSi2 has been studied for more than five decades, it was not until recently that industrial applications demanding high temperature and corrosion resistance started utilizing MoSi2 as a bulk material and a coating. Furthermore, beyond its traditional use due to its thermal properties, the most recent applications include it as a contact material in microelectronic components or circuits and optoelectronics. The short-term global growth predicted for the MoSi2 heating elements market is expected to significantly impact possible new applications, considering its potential for reuse and recyclability. A prospective assessment of the application of recycled MoSi2 to composite materials is presented.
Residual thermal stresses in MoSi2–Mo5Si3 in-situ composites
Materials Science and Engineering: A, 1999
Residual thermal stresses in MoSi 2 -Mo 5 Si 3 in-situ composites are calculated for a dilute concentration of particles of one phase embedded in a matrix of the other, using the fields of anisotropic ellipsoidal inclusions. Additionally, the eutectic interfaces are modeled as boundaries between two anisotropic half-spaces. The misorientation between MoSi 2 -Mo 5 Si 3 is obtained from the literature for Mo 5 Si 3 precipitates in MoSi 2 and by electron diffraction in the scanning electron microscope (SEM) for the opposite case. Tensile stresses of up to 3 GPa can develop after cooling from the eutectic temperature due to the thermal expansion mismatch between the phases. Electron microscopy of arc-melted Si-rich Mo 5 Si 3 shows that stresses are relieved by intergranular fracture in Mo 5 Si 3 and either dislocation plasticity or transgranular cracks in MoSi 2 , in a manner consistent with the calculations.
Ductile Phase Toughening of MoSi2-Chemical Compatibility and Fracture Toughness
MRS Proceedings, 1990
Chemical compatibility between oxide coated Nb filament reinforcements and MoSi2 was investigated. It was determined that ZrO2, Al2O3, and mullite coatings were chemically compatible with both Nb and MoSi2. Comparison between coated and uncoated filaments indicated that the coatings reduced the thickness of the interaction zone. The fracture toughness of the Nb filament reinforced composites showed an increase, while W filament reinforced composite showed a decrease, in the toughness compared to that of the matrix. The results are discussed in terms of the mismatches in the coefficients of thermal expansion and the bonding characteristics of the reinforcement/matrix interface.
Effect Of Ceramic Dispersoids On The High Temperature Strength Of Mechanically Alloyed MoSi2
MRS Proceedings, 1990
ABSTRACTMechanical alloying (MA) has been used to synthesize MoSi2 from elemental Mo and Si powders. SiC and A12O3 dispersoids were also incorporated as a means of increasing high temperature strength. After synthesis, the powders were consolidated using vacuum hot pressing. It is shown that the size and volume fraction of porosity increases anomalously with increasing hot pressing temperature over the range 1200 to 1700°C. The strengths of the A12O3 composite are, in most instances, considerably higher than the monolithic material produced under similar conditions.
2009
The present study investigates the influence of small amounts of MoSi 2 sinter-aid on the densification and high-temperature properties of TiB 2. Almost full densification of TiB 2 is achievable with 2.5 wt.% MoSi 2. The hardness of TiB 2 decreases with temperature, though the samples retained their maximum hardness of 10.5 GPa up to 900°C. A promising outcome of the present research is that the flexural strengths of TiB 2 and TiB 2-2.5 wt.% MoSi 2 have been found to increase with temperature (550 MPa at 1000°C).
On the toughening mechanisms of MoSi2 reinforced Si3N4 ceramics
Applied Physics A, 2006
The toughness increment occurring in Si 3 N 4-based composites due to the addition of MoSi 2 particles was compared to the predictions of theoretical models based on the combination of residual stresses and crack deflection toughening mechanisms. A direct application of theoretical models led to a substantial discrepancy between predicted and observed values. For this reason, the basic parameters of the theoretical models were experimentally evaluated. The residual stresses were assessed by measuring the strain in the reinforcing particles by X-ray diffraction. Moreover, the MoSi 2 interparticle distance was calculated by image analysis and the crack paths were analyzed in order to check the actual extent of crack deflection. The overall toughness increase recalculated as the sum of the newly estimated values of residual stresses and crack deflection contributions, was shown to be in good agreement with the experimental results.