Sinterforging and indentation creep of nanophase TiAl

Lisa Kim, Thomas Klassen, Robert Averback, Carl Altstetter

Research output: Contribution to journalArticlepeer-review

Abstract

Indentation creep and hot hardness of consolidated nanophase TiAl powders have been studied. In addition, deformation during unconstrained uniaxial compression (sinterforging) of green compacts has been used to derive high temperature deformation parameters for mechanically alloyed TiAl. Powders were synthesized by both vapor phase condensation of magnetron-sputtered TiAl and by ball milling of elemental powders. Production and consolidation of the powders took place under UHV conditions or purified argon. Testing took place under either vacuum or purified argon at temperatures up to 650°C. The objective was to study the processing and mechanical behavior of bulk materials with grain sizes in the nanometer range. To complement the experimental program computer simulations of powder consolidation were made. In addition to mechanical testing, calorimetric, x-ray and density measurements were combined with microscopic observations in order to characterize microstructural changes that accompanied plastic deformation. TiAl powders resulting from magnetron sputtering of TiAl and condensation of the vapor were initially amorphous, in contrast to the disordered HCP of TiAl that resulted from ball milling of titanium and aluminum powders. As formed, the grain sizes resulting from both preparation methods were in the range of 10-15 nm, as measured by x-ray line broadening. However, the ball milled particles were polycrystalline and had irregular, equiaxed shapes, whereas the spherical, vapor-condensed particles crystallized to single crystals. The round particles sintered to greater than 95% density at as low as 250°C, but the ball milled TiAl, which had lower green density, required higher temperatures to achieve this densification, even when consolidated by sinter forging. In both cases, high densities could be achieved without appreciable grain growth. In neither case was there more than a factor of five increase in grain diameter at 600°C.

Original languageEnglish (US)
Pages (from-to)881-886
Number of pages6
JournalMaterials Science Forum
Volume235-238
Issue numberPART 2
StatePublished - Jan 1 1997

Keywords

  • Indentation creep
  • Mechanical alloying
  • Nanophase
  • Sinterforging
  • Sintering
  • TiAl
  • Vapor condensation

ASJC Scopus subject areas

  • Materials Science(all)

Fingerprint Dive into the research topics of 'Sinterforging and indentation creep of nanophase TiAl'. Together they form a unique fingerprint.

Cite this