The results of structure and mechanical properties investigations of tungsten heavy alloy (THA) after cyclic sintering are presented. The
material for study was prepared using liquid phase sintering of mixed and compacted powders in hydrogen atmosphere. The specimens in
shape of rods were subjected to different number of sintering cycles according to the heating schemes given in the main part of the paper
From the specimens the samples for mechanical testing and structure investigations were prepared. It follows from the results of the
mechanical studies, that increasing of sintering cycles lead to decrease of tensile strength and elongation of THA with either small or no
influence on yield strength. In opposite to that, the microstructure observations showed that the size of tungsten grain increases with
number of sintering cycles. Moreover, scanning electron microscope (SEM) observations revealed distinctly more trans-granular cleavage
mode of fracture in specimens subjected to large number of sintering cycles compared with that after one or two cycles only.
The results of structure observations of Ni base superalloy subjected to long-term influence of high pressure hydrogen atmosphere at 750K
and 850K are presented. The structure investigation were carried out using conventional light-, scanning- (SEM) and transmission electron
microscopy (TEM). The results presented here are supplementary to the mechanical studies given in part I of this investigations. The
results of study concerning mechanical properties degradation and structure observations show that the differences in mechanical
properties of alloy subjected different temperature are caused by more advanced processes of structure degradation during long-term aging
at 850K, compare to that at 750K. Higher service temperature leads to formation of large precipitates of δ phase. The nucleation and
growth of needle- and/or plate-like, relative large delta precipitates proceed probably at expense strengthening γ" phases. Moreover, it can't
be excluded that the least stable γ" phase is replaced with more stable γ' precipitates. TEM observations have disclosed differences in
dislocation structure of alloy aged at 750K and 850K. The dislocation observed in alloy subjected to 750K are were seldom observed only,
while in that serviced at high stress and 850K dislocation array and dislocation cell structure was typical.