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Transformations, Microstructure and Properties of Nb-(10-16) At.% Al Alloys

Published online by Cambridge University Press:  28 February 2011

Sen-Shan Yang  and
Vijay K. Vasudevan
Sen-Shan Yang
Affiliation:
Department of Materials Science & Engineering, University of Cincinnati, Cincinnati,OH 45221
Vijay K. Vasudevan
Affiliation:
Department of Materials Science & Engineering, University of Cincinnati, Cincinnati,OH 45221
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Abstract

Transformations, microstructures and mechanical properties of Nb(10-16) at.% Al alloys are reported. Cast buttons of the alloys were solutionized in the high temperature single phase Nb-Al region and cooled to retain supersaturated solid solutions (SS). These SSs are observed to show B2 ordering, with both the degree of ordering and hardness increasing with increase in Al. The precipitation of ND3AI from the supersaturated SS, which was studied as a function of temperature (1000-1600°C) and time (to 100h) by hardness measurements and microscopy, is sluggish, proceeds by initial heterogeneous nucleation at grain boundaries followed by growth into the grains in a discontinuous fashion, follows C-curve kinetics, and leads to significant hardening. The size, spacing and amount of the Nb3Al precipitates depend strongly on Al content, temperature and time. The compressive yield strength of the SS increases with %Al and high values of 900 and 500 MPa at 25 and 900°C, respectively, are observed. The presence of Nb3Al leads to a very significant increase in yield strength, with values being as high as 1550 and 1100 MPa at 25 and 900°C, respectively. Also, a strong dependence of strength on the size and spacing of the Nb3Al precipitates is observed. These results are presented and discussed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 288: Symposium L – High-Temperature Ordered Intermetallic Alloys V , 1992 , 731
Copyright
Copyright © Materials Research Society 1995

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References

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