MEANS 2: Microstructure- and Micromechanism-Sensitive Property Models for Advanced Turbine Disk and Blade Systems; Final rept. 30 Sep 2004-30 Sep 2007

摘要

This effort has focused on verification and refinement of the mechanism transitions at intermediate temperatures in the disk alloy Rene 104, with the observation of microtwinning, continuous faulting and dislocation by- pass at successively higher temperatures above 650 degrees C. Evidence for the twin initiation process has also been obtained via TEM studies of specimens interrupted after small strain levels. A model for the novel microtwinning regime. Modeling at the ab initio, atomistic and phase field levels is providing insight into the activation parameters associated with the observed deformation mechanisms. Single crystals of Rene 104 have successfully been grown. A novel phase field model of directional coarsening (rafting) during high temperature, low stress creep of blade alloys has been developed. This model accounts for the local stress fields associated with matrix dislocations as well as the lattice misfit, and demonstrates promising qualitative agreement with experiment. Finally, deformation mechanisms in high temperature creep of several 'generation 4' single crystal blade alloys under rafting conditions have been studied and a model for creep under these conditions developed. The goal of the program is to develop improved models that will (a) incorporate more realistic representation of the relevant microstructures and micromechanisms, (b) enable modeling for a range of relevant service conditions (c) address time-dependent deformation in both disk and blade alloys, and (d) provide this information to the component design process, building upon the paths to the design process created in the DARPA Accelerated Insertion of Materials (AIM) program.