Compressive response of Ni45.3Ti34.7Hf15Pd5 and Ni45.3Ti29.7Hf20Pd5 shape-memory alloys

Abstract

The shape-memory properties of Ni45.3Ti34.7Hf15Pd5 and Ni45.3Ti29.7Hf20Pd5 polycrystalline alloys were determined through superelasticity and shape-memory tests in compression. It has been revealed that the Ni45.3Ti34.7Hf15Pd5 has a maximum transformation strain of 3.8 % and work output of up to 30 J cm(-3), while the Ni45.3Ti29.7Hf20Pd5 has a maximum transformation strain of 2.6 % and work output of up to 20 J cm(-3) at 700 MPa. Two-way shape-memory strains of 0.6 and 0.85 % were obtained in Ni45.3Ti34.7Hf15Pd5 and Ni45.3Ti29.7Hf20Pd5 alloys, respectively. The Ni45.3Ti34.7Hf15Pd5 showed superelasticity at 90 A degrees C with recoverable strain of 3.1 %, while high hardening of Ni45.3Ti29.7Hf20Pd5 limited its superelastic behavior. Microstructure of the Ni45.3Ti34.7Hf15Pd5 alloy was revealed by transmission electron microscopy, and effects of composition on the lattice parameters of the transforming phases and martensite morphology were discussed.