Microstructural Characterization of Ti-44Al-11Nb in the Chill-Cast and Directionally Solidified Configurations

Abstract

The microstructural evolution in chill-cast and directionally solidified Ti-44Al-11Nb (at.%) was studied by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods. From this data, the microstructural distribution and formation sequences of various phases like Al3Ti, TiAl, and Ti3Al were established. The elemental and phase distributions were determined by TEM with energy dispersive x-ray spectroscopy (EDX) and spectrum imaging. Both casting techniques produced the same phases, (Al3Ti, TiAl, and Ti3Al with some Nb in solid solution), but the microstructural distribution was markedly different. The chill-casting technique resulted in a coarser microstructure, with large gamma crystals and duplex regions of either (gamma + alpha2) or (gamma + Al3Ti) interspersed throughout the alloy. The directional solidification technique resulted in a much more uniform microstructure with fine lamellar grains in a dendritic macrostructure. Both casting techniques showed enrichment of niobium in interdendritic regions.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1998
Accession Number
ADA359595

Entities

People

  • Timothy R. Halladay

Organizations

  • Naval Postgraduate School

Tags

Communities of Interest

  • Advanced Electronics
  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Air Force
  • Alloys
  • Chemical Synthesis
  • Chemistry
  • Crystal Structure
  • Diffraction
  • Electron Microscopy
  • Materials
  • Materials Engineering
  • Mechanical Working
  • Phase Diagrams
  • Phase Transformations
  • Solid Solutions
  • Spectra
  • Tensile Strength
  • Turbines
  • X Rays

Fields of Study

  • Materials science

Readers

  • Powder metallurgy of Titanium alloys.

Technology Areas

  • Microelectronics