Wf. Gale et Zam. Abdo, Cast and aged beta-NiAl-beta '-Ni2AlTi-gamma '-Ni3Al-alpha-Cr alloys: a microstructural and mechanical properties investigation, J MATER SCI, 34(18), 1999, pp. 4425-4437
Microstructural development and stability in cast Ni-30 at % Al-21 at % Cr-
4 at % Ti, Ni-28 at % Al-18 at % Cr-6 at % Ti and Ni-26 at % Al-19 at % Cr-
8 at % Ti alloys are examined in this paper. The paper considers the extent
to which microstructural control and stability is improved in these alloys
, when compared with earlier work by the authors on similar materials with
lower aluminum (25 or 26 at %) and higher titanium (11 to 15 at %) contents
. The paper discusses detailed transmission electron microscopy investigati
ons of both as-cast and aged (140 h at 850 and 1100 degrees C) samples. Att
ention is focussed on the transformation of L2(1) type beta' (nominally Ni2
AlTi) dendrites. In particular, the influence of the formation of intradend
ritic L1(2) type gamma' (nominally Ni-3(Al,Ti)) on the stability of the bet
a'-phase is examined. Morphological changes and phase transformations withi
n a beta'-alpha-Cr eutectic are discussed. Various modes of second-phase pr
ecipitation are considered. The microstructures of selected samples are cor
related with mechanical properties determined by tensile testing and fracto
graphy. (C) 1999 Kluwer Academic Publishers.