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Deformation Behavior of Polycrystalline MoSi2 Between 495°C and 1250°C

Published online by Cambridge University Press:  10 February 2011

L. Junker ,
M. Bartsch  and
U. Messerschmidt
L. Junker
Affiliation:
Max Planck Institute of Microstructure Physics, Weinberg 2, Halle (Saale), D - 06120, Germany
M. Bartsch
Affiliation:
Max Planck Institute of Microstructure Physics, Weinberg 2, Halle (Saale), D - 06120, Germany
U. Messerschmidt
Affiliation:
Max Planck Institute of Microstructure Physics, Weinberg 2, Halle (Saale), D - 06120, Germany
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Abstract

In order to study the deformation processes of reaction-sintered and hot pressed MoSi2, compression tests have been performed and the microstructure of the deformed samples has been investigated by optical, scanning and transmission electron microscopy. At a low strain rate of 2.5× 10−7 S−1 permanent deformation has been achieved at 1250°C. The deformation behaviour is controlled by different microprocesses within different temperature ranges. Below 1000°C, hardening occurs beyond the upper and lower yield points. Inside the grains, dislocations glide at sufficiently high stresses in a homogeneous way as well as in localized slip bands. A plateau in the dependence of the yield stress on temperaturecorresponds to the flow stress anomaly of easy slip systems in single crystals. However, since there are not enough independent slip systems to satisfy the van Mises criterion, the material does not deform homogeneously in all grains. Intergranular and intragranular cracks, which are formed after the yield point, carry an increasing part of strain at decreasing temperatures. Above 1000°C, softening occurs after the yield point. A grain boundary phase flows viscously and carries most of the deformation. Since the grains do not deform themselves, intergranular cracks develop also at high temperatures.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 552: Symposium KK – High-Temperature Ordered Intermetallic Alloys VIII , 1998 , KK5.23.1
Copyright
Copyright © Materials Research Society 1999

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References

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