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The Role of Local Disorder Near Grain Boundary in Ductilization of Ni3Al

Published online by Cambridge University Press:  01 January 1992

Jian Sun
Affiliation:
Department of Materials Science and Engineering, Shanghai JiaoTong University, Shanghai 200030, P.R.China
Dongliang Lin (T.L. Lin)
Affiliation:
Department of Materials Science and Engineering, Shanghai JiaoTong University, Shanghai 200030, P.R.China
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Abstract

The local chemical order near grain boundaries (GBs) in NisAl was verified by measuring the local degree of order and chemistry with microdiffraction and EDS microanalysis. The composition of alloys are (a) Ni-24at%Al with and without 700ppm wt boron;(b) Ni-25 at%Al with 700ppm wt boron;(c) Ni-26 at%Al with 700ppm wt boron. GBs studied in the present work are high angle boundaries. The results show that there is a local disordered region about 5-10nm wide on the side of the GB in non-stoichiometric Ni3Al with or without boron, and no disordered region in stoichiometric Ni3Al. EDS microanalysis results show that the composition of GB almost keeps the matrix concentration of Ni in stoichiometric Ni3Al with boron, and is Ni-rich in hypostoichiometric and Al-rich in hyperstoichiometric Ni3Al with and without boron. The local disordered region existing in the vicinity of GBs is related to Ni enrichment or depletion near GBs in hypostoichiometric or hyperstoichiometric Ni3Al alloys. Boron seems not to be the main factor to control the local disorder and composition at GBs in Ni3Al alloys. It can be concluded that the local disorder at GBs is not a decisive factor for ductilizing GBs in Ni3Al alloys.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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