The quench-ageing behaviour of a new Co–Ni–Cr-base high-temperature alloy containing Ti has been studied. The as-quenched structure of the alloy was fcc, and on ageing between 700 and 900° C (973 and 1173 K) the main strengthening phase was observed to be an ordered fcc γ′ phase. On overageing, this phase transforms to a stable hexagonal Ni3Ti η phase. The grain boundaries provide nucleation sites for the cellular precipitation of η phase. TiC and M23C6 carbides were also observed. However, during overageing TiC transforms to M23C6 carbides.
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