IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research
IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research
IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research
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IGC<br />
<strong>Annual</strong> <strong>Report</strong> 2007<br />
austenite and the intermetallics<br />
could be observed in Fig.4.<br />
XRD technique was found to be<br />
good in quantifying austenite<br />
Fig.3 Bright field image<br />
(showing high dislocation<br />
density) specimen solution annealed<br />
at 1093 K <strong>for</strong> 1 h<br />
followed by air cooling.<br />
but was unable to determine<br />
the austenitic initiation early<br />
due to low sensitiveness of the<br />
technique <strong>for</strong> austenite volume<br />
Fig.4 Bright field image of the<br />
specimen thermally aged at 755 K<br />
<strong>for</strong> 100 h followed by water<br />
quenching, showing long and patchy<br />
austenite (marked as A), patchy<br />
Ni 3 (Ti, Mo) (marked as B) and<br />
globular Fe 2 Mo (marked as C)<br />
fraction (less than 2 %).<br />
However, XRD techniques has<br />
been used as a benchmark <strong>for</strong><br />
quantitative estimation of<br />
volume fraction of reverted<br />
austenite using MBE and EC<br />
techniques. Table 1 brings out<br />
at a glance the relative<br />
capabilities of various NDE<br />
parameters employed <strong>for</strong><br />
characterization of various<br />
microstructural features in<br />
M250 grade maraging steel.<br />
Thus, by adopting multi-NDE<br />
approach, it is possible to get a<br />
comprehensive picture of<br />
interaction of interrogating<br />
media with microstructural<br />
features towards developing a<br />
robust methodology <strong>for</strong><br />
characterization<br />
of<br />
microstructures.<br />
V.A.4. A Novel Methodology based on Ultrasonic<br />
Attenuation to Characterize the Dynamically Recrystallized<br />
Microstructure in Alloy D9<br />
A new methodology based on<br />
ultrasonic C-scan presentation<br />
has been identified to image<br />
the microstructural evolution<br />
during dynamic recrystallization<br />
(DRX) of alloy D9. Hydraulic<br />
press <strong>for</strong>ging operations were<br />
carried out on 30 mm height<br />
and 20 mm diameter<br />
compression specimens at a<br />
mean strain rate of 0.22 s -1<br />
using a 250-ton triple-action<br />
hydraulic press. Four specimens<br />
were <strong>for</strong>ged at 1273 K <strong>for</strong><br />
different strains in the range of<br />
0.1 - 0.5. The in-house<br />
(a)<br />
developed ultrasonic C-scan<br />
imaging system 'ULTIMA 200'<br />
and a 6 MHz point focused<br />
(b)<br />
Fig. 1 C-scan image of the specimens <strong>for</strong>ged at 1273 K to<br />
a stain of (a) 0.2 and (b) 0.5<br />
ENABLING TECHNOLOGIES 121
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