and molybdenum carbides (10,14) The spot towards the center also ce 
corresponds to a (Ti,Mo) carbide (10,14) which was corroded by the a 
electrolytic etching. The elongated spot to the left corresponds to So 
an inclusion of titanium sulphide (10,14) which was also corroded by Te 
the etchant. The presence of carbides in the as-forged state i 
indicates that the ingot heating time for forging was not enough for Ca 
the dissolution of those carbides, since it has been verified that Co 
after 2 hours at 1180°C the presence of carbides was not noted CL 
through the optical microscope (10), Lo 
Figure 9 shows the micrography in a homogenized 10h+aged condition oe 
by using the 4%Nital etchant. Darker regions are noted where the detern 
presence of austenite can be seen with larger magnification, as shown i 
in Figure 10. The micrography shown in Figure 9 refers to the same a 
specimen shown in Figures 2 and 4 in which the microsegregation is 
not revealed. The aged condition is that which allows for better Co 
qualitative assessment of the microsegregation degree. In the or 
homogenized 25h+aged condition it was still possible to see slightly 
darker areas etched by the 4%Nital, with 50x magnification. In this 
case, the resolution of white areas was only possible with a 1000x 
magnification as shown in Figure 11. After homogenization for 
35h+ageing, it was no longer possible to observe the presence of 
austenite through the optical microscope. Figure 12 shows the 
micrography in the homogenized 50h+aged condition. 
The results of austenite content measurements through X-ray 
diffractometry, and quantitative metallography are shown in Table I. 
These figures show that austenite was already present before ageing. 
Probably, the austenite reverted during the ingot heating for 
forging, since in an as-cast specimen taken from the bottom of the 
ingot, austenite was not detected. 
ht 19570C Ch) (as-forged) A | 35 | 20 
Not-aged 5% A ND | ND 
-ray diff. | | 
After ageing — | 
X-ray diff. \ 0.96% (*) 0-458]. 2050-214 ND | ND On 
Quant. metall. 0,99%+0.15(CI=95%) — - - = - 
TABLE I - Determination of austenite content (% vol.). (ND= non V ange 
detected). (*) Average of two determinations : 0.83% and 1.10%. To 
Prakt. Met. Sonderbd. 21 (1990) 
U, 6 
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