Lt. Shiang et Cm. Wayman, MARAGING BEHAVIOR IN AN FE-19.5NI-5MN ALLOY - I - PRECIPITATION CHARACTERISTICS (REPRINTED FROM METALLOGRAPHY, VOL 21, PG 399-423, 1988), Materials characterization, 39(2-5), 1997, pp. 529-553
The aging behavior of an Fe-19.5Ni-5Mn alloy has been studied in detai
l. A substantial maraging-hardening response was obtained upon aging a
t between 300-550 degrees C, and it displayed classical hardening beha
vior. The pronounced hardness was attributed to strain hardening cause
d by coherent, fine spherical precipitates. The activation energy for
precipitation, calculated from microhardness data, was 41 kcal/gmole.
Ordered fct theta-NiMn precipitates were identified with two different
shapes, depending on the aging temperature. Higher aging temperatures
resulted in disk-shaped precipitates, while rod precipitates appeared
at lower temperatures. Twin-related Widmanstatten austenite grains ap
peared in a lenticular shape that were coupled together by a twin boun
dary. Their orientation relationship with the parent martensite was fo
und to be of the Kurdjumov-Sachs (K-S) type.