A. Baldan, THIN-SECTION SITE AND GRAIN-SIZE DEPENDENT MONKMAN-GRANT DUCTILITY OFA NICKEL-BASE SUPERALLOY, Materials science and technology, 13(12), 1997, pp. 1033-1038
The combined effects of thin section size D and grain size d(G) (or nu
mber of grains across the gauge section n(G)) on the creep behaviour o
f conventionally cast MAR-M002 were studied for creep conditions of 90
0 degrees C and 300 MPa. It was observed that there was a linear corre
lation between the t(R)/d(G) and epsilon(m)/D ratios on log-log scales
(the modified Monkman-Grant relationship), where t(R) is the creep ru
pture life and epsilon(m) is the minimum creep rate. The Monkman-Grant
ductility t(R) epsilon(m) showed a rapid improvement with increasing
D-2/n(G) ratio. It is concluded that the existence of the modified Mon
kman-Grant relationship is due to the coupling of the creep deformatio
n in the secondary region through grain boundary sliding with the cree
p crack growth behaviour int he tertiary region. (C) 1997 The Institut
e of Materials.