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The assessment of compositional changes in Nimonic PE16 by convergent beam electron diffraction
Author(s) -
Randle Valerie,
Ralph Brian
Publication year - 1987
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1111/j.1365-2818.1987.tb02841.x
Subject(s) - nimonic , electron diffraction , materials science , grain boundary , lattice (music) , precipitation , diffraction , intergranular corrosion , lattice constant , electron backscatter diffraction , crystallography , condensed matter physics , microstructure , metallurgy , chemistry , superalloy , physics , optics , meteorology , acoustics
Lattice parameter changes can be detected by the use of a previously established technique which is based upon computer simulation of HOLZ patterns. This simulation technique is then applied to two precipitation phenomena in Nimonic PE16. Firstly, the growth of gamma prime, γ, precipitates from a solid solution is monitored via the decrease in lattice parameter of the parent phase, and secondly the lattice parameter of coarsened, overaged γ is measured for precipitates sited both at grain boundaries and within grains. The variations thus detected between intergranular and intragranular precipitates are attributed to changes in the Ti/Al ratio due to preferential γ coarsening at the grain boundary. The very subtle compositional changes inferred (∼1 at. % Ti) would have been very difficult to establish by chemical analysis, but can be easily measured by convergent beam electron diffraction.