Abstract
Four different types of specimens were prepared from the center and the
periphery of two large IN706 forged discs of commercial scale, and low
cycle fatigue (LCF) tests were conducted at 650 oC.
The IN706 specimens with lower LCF lives showed relatively large
fraction of cleavage-like fracture along linearly aligned η (Ni
3Ti) precipitates in the area of crack propagation. The
amount of η precipitates for those specimens with greater LCF lives was
negligible, and the fracture mode of crack propagation was dominantly
intergranular. Crack initiation was mainly by persistent slip band (PSB)
cracking at the surface, and no notable difference was found for each
specimen. The correlation between tensile properties, grain size and LCF
lives of IN706 at 650 oC appeared to be not as
significant as expected.