Analysis of Deformation Substructures in a Notched LCF Sample Under Dwell Condition in a Ni-Based Superalloy (PREPRINT)

Detailed transmission electron microscopy (TEM) studies were conducted on LCF Rene 104 alloy samples tested under dwell conditions to analyze the deformation substructures. Specifically, the focus was to investigate the effect of crack length, in other words, stress intensity factor range deltaK, on the deformation substructures. Thin foils were prepared by focused ion beam method (FIB) from two specific grains along the crack path at varying distances representing varying K values. The TEM analysis indicated that the character of deformation substructures significantly differed in these two grains. It is therefore speculated that local stress conditions and the grain orientations played a key role in the damage accumulation and subsequent substructure evolution. The regions below the fracture surface also investigated were. Detailed scanning electron microscopy (SEM) investigations of the grains immediately below the fracture surface revealed extensive microstructure degradation and potential hot spots for crack nucleation. Prepared in collaborartion with Metals Branch (RXCM), Structural Materials Division, Air Force Research Laboratory, GE Aviation, and Ohio State University. Preprint to be submitted to Superalloys 2012. This document contains color.