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Amorphous phase separation in a shock consolidated glass-forming Ni_(55.8)Mo_(25.7)Cr_(9.7)B_(8.8) alloy powder

Thadhani, Naresh N. and Mutz, Andrew H. and Vreeland, Thad, Jr. (1986) Amorphous phase separation in a shock consolidated glass-forming Ni_(55.8)Mo_(25.7)Cr_(9.7)B_(8.8) alloy powder. Scripta Metallurgica, 20 (4). pp. 581-586. ISSN 0036-9748. doi:10.1016/0036-9748(86)90258-9.

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Amorphous phase separation upon quenching of the melt has been a common observation in ceramic glasses, and has been extensively reviewed by Uhlmann and Kolbeck (1). Although similar observations have been cited (2-10) in amorphous metallic systems, the presence of a two phase glass microstructure is still being debated. Phase separation in amorphous metals is also known to occur during quenching from the melt, but more generally during reheating of single phase glasses. The separated amorphous phase then acts as a precursor to subsequent crystallization. The phenomenon of phase separation evidenced by transmission electron microscopy (TEM) images and microchemical analysis has also been complemented by differential thermal analysis (OTA). However, a mechanistic understanding of the process of separation is still lacking. In this note we report the observation of a spherically shaped glassy phase in amorphous regions formed from rapid solidification of the melt at interparticle boundaries, in a shock consolidated Markomet 1064 (Ni_(55.8)Mo_(25.7)Cr_(9.7)B_(8.8)) alloy powder . It has been shown (11) that during dynamic consolidation of this glass forming alloy powder, the shock energy is preferentially utilized in heating (due to plastic deformation) and subsequent melting of interparticle surfaces. The melted regions rapidly resolidify, due to heat flow towards relatively cool particle interiors, and form amorphous material. Some of the melted regions cool sufficiently slowly to result in the formation of a two phase amorphous microstructure. This note presents TEM micrographs showing typical morphology of the separated amorphous phase. Differential thermal analysis (OTA) and semi-quantitative micro-chemical analysis supporting the microstructural observations are also reported.

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Additional Information:© 1986 Pergamon Press Ltd. Received January 9, 1986. This research was supported in part by the National Science Foundation under Grant No. DMR-8315214 and the Caltech Program in Advanced Technologies, sponsored by Aerojet General, General Motors, GTE and TRW. Shock consolidation experiments were performed in Prof. Thomas Ahrens' Seismo-Laboratory at Caltech. The help of Mr. Patrick Koen, Caltech, and Mr. Jack Warrel, University of Southern California, in the electron microscopy work is gratefully acknowledged. Appreciation is also extended to Ms. Lynn E. Lowry, Jet Propulsion Laboratory for performing the OTA measurements.
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Caltech Program in Advanced TechnologiesUNSPECIFIED
Aerojet GeneralUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20150316-102019312
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Official Citation:Naresh N. Thadhani, Andrew H. Mutz, Thad Vreeland Jr., Amorphous phase separation in a shock consolidated glass-forming Ni55.8 Mo25.7 Cr9.7 B8.8 alloy powder, Scripta Metallurgica, Volume 20, Issue 4, April 1986, Pages 581-586, ISSN 0036-9748, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55780
Deposited By: Tony Diaz
Deposited On:16 Mar 2015 17:38
Last Modified:10 Nov 2021 20:50

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