Abstract
The precipitation of the intermetallic γ′ phase and of carbide phases in the NiCu-base aluminium- and titanium-bearing age-hardenable alloy Monel K-500 has been investigated, using transmission electron microscopy. It was found that the γ′ particles nucleate homogeneously and remain spherical in shape and coherent with the matrix even after prolonged aging. The coarsening kinetics of these precipitates were examined and a linear dependence of the average precipitate radius on the cube root of the aging time was observed. The principal carbide phase in this alloy was identified as a titanium-rich MC-type phase, coarse particles of which are distributed in a non-uniform manner within the grains and also at the grain boundaries. In addition, a grain boundary carbide phase, isostructural with Cr23C6, was found to form in this chromium-free alloy on aging.
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