Effect of nanocrystallization and twinning on hardness in Ni 3AI deformed by high-pressure torsion

Octav Ciuca, Koichi Tsuchiya, Yoshihiko Yokoyama, Yoshikazu Todaka, Minora Umemoto

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


Samples of Ni 3AI intermetallic compound were subjected to deformation by high-pressure torsion (HPT). The plastically-deformed structure revealed a bimodal character: coarse grains, retaining a degree of long-range order, surrounded by regions of nanocrystalline, disordered grains. It was inferred that the grain refinement proceeds in an inhomogeneous manner throughout the sample. Grains as large as 100 nm in size were shown to contain only a low density of perfect dislocations, but a large density of nanotwins and stacking faults. These planar defects appeared to originate from the grain boundaries, suggesting that grain boundaries are active sources for Shockley-partial dislocations. Their formation is accompanied by a deviation of the microhardness dependence on grain size from the Hall-Petch behavior, potentially suggesting the activation of a deformation mechanism different from the one acting in coarse structures. The hardness saturates at a significantly larger grain size than in the case of nanostructured pure Ni.

Original languageEnglish
Pages (from-to)1123-1127
Number of pages5
JournalMaterials Transactions
Issue number5
Publication statusPublished - 2009 May
Externally publishedYes


  • Hall-Petch effect
  • Nanocrystalline materials
  • Shockley-partial dislocations
  • Stacking faults

ASJC Scopus subject areas

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


Dive into the research topics of 'Effect of nanocrystallization and twinning on hardness in Ni 3AI deformed by high-pressure torsion'. Together they form a unique fingerprint.

Cite this