Shape Memory Effect in Quaternary NiTiHfPd Shape Memory Alloys beyond 200 °C

Soheil Saedi, Guher P. Toker, Hatim Raji, Emre Acar, Fumiya Watanabe, Haluk Karaca

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


In this study, the effects of minor palladium (3 and 5 at.%) addition to ternary NiTiHf shape memory alloy (SMA) were investigated to design a high-temperature NiTiHfPd SMA. While most of the reported NiTiHfPd SMAs contain (Ni+Pd)-rich compositions, the (Ti+Hf)-rich compositions have not been studied to the same extent. This study investigates two new NiTiHfPd compositions and their shape memory effect at elevated temperatures. To this end, two Ni47.3Ti29.7Hf20Pd3 and Ni44.3Ti31.7Hf20Pd5 alloys were fabricated and characterized in terms of microstructure, transformation temperatures, and shape memory behavior in as-cast and aged conditions. The results demonstrated that even a minor addition of Pd could drastically alter the operating temperatures and shape memory effect of NiTiHf SMAs. The metallographic studies revealed the presence of a high volume fraction of secondary phases in the microstructure of Ni44.3Ti31.7Hf20Pd5 that consequently created a matrix leaner in (Ti+Hf) compared to Ni47.3Ti29.7Hf20Pd3. As a result, the Ni44.3Ti31.7Hf20Pd5 was found to be more responsive to precipitation hardening. The evaluation of the shape memory effect of the alloys displayed remarkable strength and strain recovery capability of the quaternary NiTiHfPd at a temperature range above 200 °C with thermal hysteresis as small as 25 °C.

Original languageEnglish
Pages (from-to)6689-6696
Number of pages8
JournalJournal of Materials Engineering and Performance
Issue number8
StatePublished - Aug 2022

Bibliographical note

Funding Information:
This research is partially supported by the National Science Foundation under Grant Number CMMI-1538770 and partially by UA-Little Rock’s signature experience program.

Publisher Copyright:
© 2022, ASM International.


  • high-temperature alloy
  • martensitic transformation
  • quaternary alloys
  • shape memory alloys
  • ultra-high strength alloys

ASJC Scopus subject areas

  • Materials Science (all)
  • Mechanics of Materials
  • Mechanical Engineering


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