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· The C-C-T "start"
and "finish" contours are shifted to longer times and lower temperatures
than those of a T-T-T diagram.
· For
cooling rates greater than 140 C/sec, austenite
is retained until
the MS-temperature
and martensite
forms below this temperature.
· Between 140 C/sec and 35 C/sec, a mixture
of martensite and the thermodynamically stable pearlite
forms. No bainite
is formed
in this alloy because transformation occurs above the "nose" of
the curve.
· Below 35 C/sec
a completely pearlite micro-structure forms. Grain
size is cooling rate dependent
with larger grains corresponding to slower cooling rates. Material hardness
decreases
as the grain size increases.
· Additional
microstructural control can be achieved by converting the
metastable martensite to pearlite by subsequent heat treatment of the alloy.
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