1995 Volume 35 Issue 9 Pages 1115-1120
The age hardening behavior and microstructural characteristics of a 53Ni-20Co-5Mo-4.9Al-1.3Ti alloy has been investigated by micro-Vickers hardness test and transmission electron microscopy. The shape of γ' precipitates was spherical at the early stage of aging and was cuboidal at the later stage. The aged hardness of the alloy closely related to the size and the quantity of γ' precipitates. The γ' precipitation cannot be suppressed by water quenching after solution treatment. It is necessary to cool the specimen at rates of higher than 104 K/s for restraining the precipitation of γ' phase. The growth kinetics of γ' precipitates in the alloy followed the prediction of Lifshitz-Slyozov-Wagner (LSW) theory for growth under volume diffusion control at all aging temperatures examined. The activation energy for the growth was estimated to be 266 kJ/mol which was close to those of diffusion of solute atoms such as Al, Ti and so on in Ni and Ni-base alloys. The actual particle size sidtribution of γ' precipitates was somewhat different from distributions predicted by the LSW and Brailsford-Wynblatt encounter modified (BWEM) theories.
