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Indexed by:期刊论文

Date of Publication:1993-05-01

Journal:JOURNAL OF THE JAPAN INSTITUTE OF METALS

Included Journals:SCIE

Volume:57

Issue:5

Page Number:582-590

ISSN No.:0021-4876

Key Words:NIAL; INTERMETALLIC COMPOUND; CREEP; BORON ADDITION; OFFSTOICHIOMETRY

Abstract:The effects of deviation from stoichiometry and addition of boron have been investigated on the creep behaviour of NiAl. It is found that the creep behaviour of near stoichiometric NiAl alloys is of the class II type with a stress exponent, n, being 4.5, while that of off-stoichiometric alloys of the class I type with n being 3.5. The activation energy for creep, Q(C), decreases with increasing Al concentration at the Ni-rich side of offstoichiometry but vice versa on the Al-rich side of offstoichiometry. At near stoichiometry, the values for the Q(C) are off the relation being found at offstoichiometry and are almost constant within 1 at% on both sides of stoichiometry. The Q(C) seems to correspond to the value of the activation energy for self diffusion of Ni at near stoichiometry and to that for interdiffusion at offstoichiometry.
   The effect of boron addition is found to increase the creep resistance of NiAl alloys at Ni-rich side of offstoichiometry without an appreciable change in the stress exponent. The reason for the enhancement of creep resistance should be due to the solution hardening by boron. At Al-rich side of offstoichiometry, no effect on the creep resistance is found by the boron addition.