日本金属学会誌

J. Japan Inst. Metals, Vol. 60, No. 6 (1996),
pp. 582-588

Activated Slip Systems in β-Silicon Nitride during High Temperature Deformation

Kouichi Kawahara, Sadahiro Tsurekawa and Hideharu Nakashima

Department of Materials Science and Technology, Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka, 816, Japan

Abstract:

In order to clarify the activated slip systems of β-silicon nitride (Si3N4) during high temperature deformation, we have studied the dislocation structures in hot-pressed β-Si3N4 deformed at temperatures from 1820 to 2020 K with strain rates from 9{×}10-6 to 2{×}10-4 s-1.
Analysis of the dislocations by transmission electron microscopy revealed that the most of dislocations in β-Si3N4 plasticaly deformed at high temperatures were c dislocations which were mobile on the {1010} as a primary slip plane. Moreover, a dislocations on the {1010} slip plane were also found to be mobile. The density of a dislocations to that of c dislocations was roughly estimated to be the ratio of 1 : 10, irrespective of the deformation condition. In addition, (a+c) dislocations gliding on the {1121} pyramidal plane were seen to be activated only under the limited deformation conditions at which β-Si3N4 showed a fairly good ductility without crack formation. The density of (a+c) dislocations was about two orders of magnitude lower than that of c dislocations.


(Received January 19, 1996)

Keywords:

silicon nitride, transmission electron microscopy, weak-beam method, c dislocation, a dislocation, (a+c) dislocation, prism slip system, pyramidal slip system


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