Finite element modeling of creep deformation in dendritic alloys

Daniel F.T. Rosenthal, David C. Dunand*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Finite element modeling is used to simulate the secondary creep rate of alloys with an inhomogeneous distribution of nano-precipitates, located within colonies of long, parallel dendrites, due to elemental segregation during directional solidification. Three-dimensional, periodic unit cells are created to approximate the aligned dendritic microstructure, with cylindrical dendrites (with high creep resistance due to nanoprecipitates) embedded within a precipitate-free matrix (with low creep resistance). Using creep power-laws for the precipitate-free matrix and the precipitation-strengthened dendrites, the creep rate of a dendritic aluminum alloy is computed for various dendrite geometry and volume fraction. When stress is applied parallel to the dendrite long axis, calculated creep rates are in reasonable agreement with creep measurements, at 300 °C, of a dendritic Al-0.07Sc-0.05Zr (at.%) alloy consisting of a pure Al matrix containing 50–60 vol% dendrites strengthened with L12-Al3(Sc,Zr) nanoprecipitates. Calculations for cases where aligned, cylindrical dendrites are ridged (emulating dendritic stubs) or bridged (emulating secondary arms) predict that these dendritic geometries, at constant volume fraction and parallel loading, strengthen less efficiently the matrix as compared to uniform cylindrical dendrites, reflecting a less effective load transfer between the two phases. When stress is applied perpendicular to the dendrites, the creep response becomes dominated by the matrix which shows higher stresses than under parallel loading, leading to much higher alloy creep rates. Alloys with bridged dendrites show the lowest perpendicular strain rate due to the alignment of the secondary arms (bridges) with the applied load, increasing load transfer to the precipitation-strengthened dendrites.

Original languageEnglish (US)
Article number142171
JournalMaterials Science and Engineering A
Volume831
DOIs
StatePublished - Jan 13 2022

Keywords

  • Aluminum alloys
  • Creep
  • Finite element analysis
  • Superalloys

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Fingerprint

Dive into the research topics of 'Finite element modeling of creep deformation in dendritic alloys'. Together they form a unique fingerprint.

Cite this