Mechanisms of Recrystallization in Superalloys
Abstract
This report results from a contract tasking Ecole des Mines de Saint-Etienne (ENSM-SE) as follows: The project will study the effects and influence of very low (50 -100 ppm) and very high (10-15%) niobium content in solid solution. Quantitative analysis of the stress-strain relationship will be conducted to determine stress-strain curves (up to large strains) at various temperatures and strain rates (typical ranges: 800 to 1000 deg. C, 0.01 to 1 s-1). Beyond the overall strain rate sensitivity (m) and apparent activation energy (Q), strain hardening (h) and dynamic recovery (r) parameters will be extracted from the data using one of the available physical equations. Evolutions of the above rheological parameters with Nb content for given straining conditions will therefore be deduced and compared with that of industrial grades. Electron Backscattering Diffraction imaging will be used to determine the Dynamic Recrystallization mechanisms operating in the various cases. Deformation microstructures will be characterized quantitatively (grain or crystallite size distributions, misorientation distributions, crystallographic texture). Such data will be put into correlation with the associated hot deformation flow stress (Derby diagrams). Two or three different states likely to be associated with precipitation of Ni3Nb will first be selected from the stress-strain curve shapes and microhardness measurements. Transmission Electron Microscopy will then be used to determine the nature, size, morphology and localization of the intermetallic (Ni3Nb) particles after straining followed by quench. In particular, their possible interactions with dislocations and grain boundaries will be analyzed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2007
- Accession Number
- ADA524284
Entities
People
- Frank J. Montheillet
- J. Le Coze