Precipitation in Ni-Co-Al alloys

The Growth of .GAMMA.' Precipitates in a 53Ni-20Co-15Cr Superalloy.

“…Many of these alloys are strengthened by fine particles of L12 type orderd y ' [Ni3(Al, Ti)] phaseprecipitated coherently with the matrix.1) Understanding of precipitation and growth of the y' phase is indispensable for development and improvement of such alloys. The present understanding is that higher contents of cobalt are effective in improving their high temperature strength becauseof an increase in the volume fraction of y' precipitates2) and a decrease both in growth rate of y' precipitates2, 3) and in stacking fault energy of the matrix. 4) The present authors have reported the precipitatijon and growth behavior of y' and y" phases in nickel-, 5,6) nickel iron-7) and iron-base8) multi component heat resistant alloys.…”

Experimental evaluation of particle coarsening theories

“…Davies et al 12 suggested that such particles would not coalesce, at least in the early stages of coarsening during which the particles are still coherent with the matrix, because the amount of energy required for an APB to form is fairly high (220 mJ m-2 ) in comparison with the interfacial energy. 13 No APBs were observed in the odd shaped particles.…”

Coarsening of γ′-precipitates in single-crystal superalloy SRR 99

“…The occasional occurrence of elongated and L-shaped precIpItates which cOatibe seen in Fig. 2 is indicative of precipitate coalescence taking place, as has been reported previously by Davies et al 2,9 The microstructures produced by aging at 900°C differ from those produced at 1100°C and shown in Fig. 1.…”

“…All the theories for the kinetics of coarsening predict that w should change with aging time t according to (2) To determine the best-fitting values of the constants nand K n a least-squares technique was employed. A logarithmic form of equation (2) was taken, such that log (wn-wo) = log Kn+log t ....…”

“…Davies et al 2 observed the formation of plates of i aligned along <lOa) directions while in a different series of superalloys Ricks et al 3 demonstrated the degeneration of the cuboidal morphology into faceted "I' -dendrites.…”