On the ductile-to-brittle transition temperature in MoSi[sub 2]

Journal Article · Wed Apr 01 00:00:00 EST 1992 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(92)90224-3· OSTI ID:6906604

Aikin, Jr, R M ^[1]

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1. Martin Marietta Lab., Baltimore, MD (United States)

This paper reports that the intermetallic compound MoSi[sub 2] combines excellent oxidation resistance, a high melting point (2020[degrees]C), reasonable strength and density, and good thermal conductivity, making it a promising material for structural applications above 1200[degrees]C. The ductile-to-brittle transition temperature of MoSi[sub 2] is generally believed to be about 1000[degrees]C, above which the material is reported to deform plastically. However, according to some recent four-point flexural test results, the transition temperature could be much higher, in the range 1300 to 1400[degrees]C. The tensile properties of hot pressed MoSi[sub 2] with two different grain sizes and a density of 94% of theoretical has been reported as a function of temperature. Both materials contained large amounts of a second phase, presumably silica. For the small-grained material, plastic elongations were undetectable at room temperature and 1090[degrees]C, 0.1% at 1204[degrees]C, and 0.5% at 1316[degrees]C. For the larger grained material, no plastic elongation was measured up to the maximum test temperature of 1316[degrees]C. Transmission electron microscopy of deformed single crystals and polycrystal samples (containing SiC whiskers) [11] reveals significant dislocation activity at elevated temperatures. Although aspects of the deformation substructure of MoSi[sub 2] is an area of active research, and some controversy, some of the results suggest increased plasticity at temperatures above 1300[degrees]C. UmaKoshi and co-workers [9,10] report that slip on <331> is activated at low temperatures for single crystals deformed in compression. At 1300[degrees]C, they report a sharp increase in compressive ductility and <100> and <110> slip. Further they observe that the climb and the mobility of these <100> and <110> dislocations are very high.

• OSTI ID: 6906604
• Journal Information: Scripta Metallurgica et Materialia; (United States), Vol. 26:7; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
INTERMETALLIC COMPOUNDS
CORROSION RESISTANCE
DENSITY
FLEXURAL STRENGTH
MELTING POINTS
THERMAL CONDUCTIVITY
MOLYBDENUM SILICIDES
DUCTILE-BRITTLE TRANSITIONS
TRANSITION TEMPERATURE
MECHANICAL PROPERTIES
MONOCRYSTALS
POLYCRYSTALS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 1000-4000 K
TRANSMISSION ELECTRON MICROSCOPY
ALLOYS
CRYSTALS
ELECTRON MICROSCOPY
MICROSCOPY
MOLYBDENUM COMPOUNDS
PHYSICAL PROPERTIES
REFRACTORY METAL COMPOUNDS
SILICIDES
SILICON COMPOUNDS
TEMPERATURE RANGE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
360203* - Ceramics
Cermets
&amp; Refractories- Mechanical Properties
360202 - Ceramics
Cermets
&amp; Refractories- Structure &amp; Phase Studies
360204 - Ceramics
Cermets
&amp; Refractories- Physical Properties