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Relationship Between High-Strain-Rate Superplasticity and Interface Microstructure in Aluminum Alloy Composites

Published online by Cambridge University Press:  02 July 2020

J. Koike ,
K.E. Sickafus  and
T.E. Mitchell
J. Koike
Affiliation:
Dept. of Materials Science, Tohoku University, Sendai, 980-8579, Japan
K.E. Sickafus
Affiliation:
Materials Science and Technology Division, Los Alamos National Laboratory
T.E. Mitchell
Affiliation:
Center for Materials Science, Los Alamos National Laboratory, Los Alamos, NM87535
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Extract

The Al alloy composites reinforced with Si3N4 or SiC have been reported to exhibit superplasticity at high strain rate of faster than 1x10−2 s−1. It has been shown in many aluminum alloy composites that the optimum superplastic temperature coincides with an incipient melting temperature. The coincidence suggests a contribution of the liquid phase to the superplasticity mechanism. This paper shows a direct evidence of partial melting along matrix grain boundaries and matrix-reinforcement interfaces. Based on the obtained results, the role of the liquid phase in the high-strain-rate superplasticity is discussed.

The sample was Al-Mg (5052) alloy reinforced with 20vol% Si3,N4 particles, fabricated by a powder metallurgy process. The sample showed an excellent superplasticity under the conditions given in Table 1. Partial melting was confirmed to occur at 821 K by differentail scanning calorimetry. The microstructural changes during heating were observed in situ by TEM using a heating stage. The structure of interfaces and grain boundaries was observed by HREM. Chemical analysis was performed with EDS attached to VG-STEM.

Type
Future of Microscopy: Ceramics, Composites, and Cement
Information
Microscopy and Microanalysis , Volume 5 , Issue S2: Proceedings: Microscopy & Microanalysis '99, Microscopy Society of America 57th Annual Meeting, Microbeam Analysis Society 33rd Annual Meeting, Portland, Oregon August 1-5, 1999 , August 1999 , pp. 772 - 773
Copyright
Copyright © Microscopy Society of America

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References

This research was supported by the US DOE, OBES and by Japanese Ministry of Education.