Accession Number : AD0439216

Title :   PEST REACTIONS IN INTERMETALLIC COMPOUNDS. II. INVESTIGATIONS ON NIAL, AND TWO MOSI2 STRUCTURES.

Descriptive Note : Rept. for Feb 63-Feb 64,

Corporate Author : GENERAL ELECTRIC CO SCHENECTADY N Y

Personal Author(s) : Seybolt,A. U. ; Westbrook,J. H.

Report Date : APR 1964

Pagination or Media Count : 46

Abstract : The grain boundary hardening phenomena investigated earlier in the case of the intermetallic compound NiGa have been found to occur in much the same manner in NiAl. As before, an oxygencontamination heat treatment followed by a sufficiently high temperature quench shows no hardening, but subsequent lower temperature aging sets up hardening. Hardening occurs in the bulk as well as along grain boundaries, but generally the effect is harder to observe in the former case because of shallow oxygen penetration in the bulk as compared to the grain boundaries. A vacancy-oxygen atom interaction model is suggested as a likely explanation for the observed hardening. Some observations have been made on pest failure in MoSi2, and grain boundary hardening in the structural analog CrAl2. It is difficult to find suitable experimental techniques to study the pest failure of MoSi2. As-cast material is more susceptible to pest failure than MoSi2 coatings on molybdenum sheet. (Author)

Descriptors :   (*ALUMINUM ALLOYS, MECHANICAL PROPERTIES), (*NICKEL ALLOYS, BRITTLENESS), (*MOLYBDENUM COMPOUNDS, HARDENING), SILICIDES, CHROMIUM ALLOYS, GRAIN BOUNDARIES, OXYGEN, DIFFUSION, CRYSTAL DEFECTS, DEGRADATION, HEAT TREATMENT, ELECTRON MICROSCOPY, X RAY DIFFRACTION, METALLOGRAPHY

Distribution Statement : APPROVED FOR PUBLIC RELEASE