Superplastic Deformation Mechanisms of Monolithic Intermetallics

W. Y. Kim, Y. Sato, S. Semboshi, S. Hanada, H. Kokawa

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Superplastic deformation behavior and microstructural evolution were investigated using typical monolithic intermetallics, L12 ordered Co3Ti (Co-22mol%Ti), B2 ordered Fe3Si (Fe-14mol%Si) and Fc3Al (Fc-28mol%Al), and D03 ordered Fe3Si (Fc-18mol%Si). Superplastic elongation in Co3Ti polycrystals increases with decreasing initial grain size. A grain boundary sliding-based mechanism is found to be responsible for the superplastic deformation. B2 ordered Fc3Si and D03 ordered Fe3Si polycrystals, which deform by <111> and <100> slip, respectively, exhibit superplasticity even though their initial grains are coarse. Dynamically recrystallized (DRX) grains with an appropriate size (e.g., of about 40 [im for Fe-18Si), which contain subgrains, are evolved during supcrplastic deformation. The formation of finer DRX grains less than 10 urn in deformation at low temperatures and high strain rates does not lead to large elongation because of high flow stress. Fe3Si single crystals also exhibit superplasticity, and subgrain structure is evolved without inducing DRX. Thus, superplasticity in Fe3Si polycrystals is closely related to the formation of subgrain structures. It is found that there are two types of superplasticity in monolithic intermetallics. At a temperature range where superplasticity appears, Fe3Si and Fc3Al single crystals have low yield stress due to easy glide and climb motion of dislocations, while Co3Ti single crystals have high yield stress due to positive temperature dependence of flow stress. Among intermetallics which have been found to show superplasticity, FeAl and Fe3(Al, Si) belong to the former type, and Ni3Al and Ni3(Si, Ti) do to the latter type. Based on the obtained results on superplasticity in monolithic intermetallics together with reported references, superplastic deformation mechanisms will be discussed.

Original languageEnglish
Pages (from-to)147-154
Number of pages8
JournalMaterials Science Forum
Publication statusPublished - 1999


  • Dynamic Recrystallization
  • Grain Boundary Sliding
  • Intel-metallic
  • Microstructure
  • Subgrain


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