Journal of Materials Engineering and Performance

, Volume 23, Issue 4, pp 1408–1414 | Cite as

Formation of the Nanocrystalline Structure in an Equiatomic NiTi Shape-Memory Alloy by Thermomechanical Processing

  • E. Mohammad Sharifi
  • A. Kermanpur
  • F. Karimzadeh
  • A. Esmaili
Article

Abstract

The microstructural evolution during cold rolling followed by annealing of an equiatomic NiTi shape-memory alloy was investigated. The high purity Ni50Ti50 alloy was cast by a copper boat vacuum induction-melting technique. The as-cast ingots were then homogenized, hot rolled, and annealed to prepare the suitable initial microstructure. Thereafter, annealed specimens were cold rolled up to 70 % thickness reduction at room temperature. Post-deformation annealing was conducted at 400 °C for 1 h. The microstructure was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and differential scanning calorimetry techniques. The initial microstructure was free from segregation and Ti- or Ni-rich precipitates and was composed of coarse grains with an average size of 50 μm. The cold rolling of NiTi alloy resulted in a partial amorphization and the deformation-induced grain refinement. A nanocrystalline structure with the grain size of about 20-70 nm was formed during the post-deformation annealing.

Keywords

induction melting nanocrystalline structure NiTi shape-memory alloy thermomechanical processing 

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Copyright information

© ASM International 2013

Authors and Affiliations

  • E. Mohammad Sharifi
    • 1
  • A. Kermanpur
    • 1
  • F. Karimzadeh
    • 1
  • A. Esmaili
    • 1
  1. 1.Department of Materials EngineeringIsfahan University of TechnologyIsfahanIran

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