Alloying behaviour of Ni3Al, Ni3Ga, Ni3Si and Ni3Ge

Precipitation hardening of superalloys by ordered γ′-particles

The physical and mechanical metallurgy of Ni3Al and its alloys is reviewed Emphasis is on developments within the past five years, a period of extremely rapid growth in research on the behaviour of this unusually interesting intermetallic compound This review is particularly concerned with solute effects on properties such as diffusion rates, ductility, fatigue resistance, and environmental stability, subjects that only recently have received much attention Novel processing techniques, including rapid solidification and powder processing, are shown to have played a key role in providing Ni3Al-base alloys with improved properties An assessment of needed areas of research to hasten commercial applications of Ni3Al alloys concludes the review

Physical and mechanical metallurgy of Ni3Al and its alloys

Microstructural and compositional design of Ni-based single crystalline superalloys ― A review

Influence of uniaxial stress on the morphology of coherent precipitates during coarsening—elastic energy considerations

The influence of 1, 3, and 5 at. pct Mo on the γ’precipitate has been studied in experimental wrought nickel-base superalloys containing about 14 at. pct Cr and 6-1/2, 9, or 12 at. pct Al, or 2 at. pct Al plus 4 at. pct Ti. Concentrations of all other elements were quite low to limit the observed effects to those of molybdenum alone. Molybdenum markedly increases the γ’ solvus temperature, as determined by the sensitive and relatively simple technique of differential thermal analysis; correspondingly, the weight fraction of γ’ increases with molybdenum additions for a given aging treatment. Molybdenum dissolves extensively in the γ’of the titanium-free alloys, but it dissolves to a considerably smaller extent in the γ’of the titanium-bearing alloys. Molybdenum substitutes for chromium in y’, but does not alter the aluminum or titanium contents of this phase. Lattice parameters of both the matrix and the γ’are increased markedly by molybdenum, in proportion to the molybdenum contents of these phases. The resulting effects on lattice-parameter mismatch correlate rather well with observed γ’morphology, which tends to change from spheroidal to cuboidal in titanium-free alloys, and from cuboidal to spheroidal in 2 at. pct Al-4 at. pct Ti alloys, as molybdenum is added to these alloys.

D. L. Sponseller

Papers

The influence of molybdenum on the γ/’phase in experimental nickel-base superalloys