High temperature shape memory behavior of Ni47.3Ti29.7Hf20Pd3 alloys

ACAR E., Toker G. P., Kurkcu H., Karaca H. E.

INTERMETALLICS, cilt.111, 2019 (SCI-Expanded) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 111
  • Basım Tarihi: 2019
  • Doi Numarası: 10.1016/j.intermet.2019.106518
  • Dergi Adı: INTERMETALLICS
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Anahtar Kelimeler: Shape memory alloys, NiTiHfPd, High strength, High temperature shape memory alloys, Class II transformation, FE-PT ALLOYS, MARTENSITE-TRANSFORMATION
  • Erciyes Üniversitesi Adresli: Evet

Özet

The shape memory properties of Ni47.3Ti29.7Hf20Pd3 alloys were investigated through stress-free thermal cycling, constant-stress thermal cycling and constant-temperature stress cycling experiments. The alloys showed reversible phase transformations above 180 degrees C, which makes them suitable for high temperature shape memory applications. Constant-stress thermal cycling experiments revealed that recoverable strains of about 2% were possible under compressive stress levels higher than 700 MPa and both the recoverable strain and thermal hysteresis values were strong functions of applied stress. Additionally, two-way shape memory strain of 0.7% was observed. Unlike most of the shape memory alloys that have Class I transformation, Class II transformation was observed in these alloys and its relationship to the elastic energy storage was discussed through thermoelastic martensitic transformation thermodynamics approach.