Characterization of the shape memory properties of a Ni45.3Ti39.7Hf10Pd5 alloy

Highlights: •Ni45.3Ti39.7Hf10Pd5 alloys have transformation strain of up to 4.6% and work output of up to 29 J cm−3. •The alloy showed good superelastic behavior at 90 °C with recoverable strain of 4.3%. •The alloy exhibited 1.6% two-way shape memory strain after a simple training procedure. •The formation of 〈0 1 1〉 type II twins in martensite plates results in large transformation strain. -- Abstract: The load-biased shape memory and superelastic responses of a Ni45.3Ti39.7Hf10Pd5 polycrystalline alloy were investigated in compression. Transformation strain of up to 4.6% and work output of up to 29 J cm−3 were determined from load-biased thermal cycling experiments. The alloy showed good superelastic behavior at 90 oC with recoverable strain of over 4%. It was also determined that the Ni45.3Ti39.7Hf10Pd5 alloy could develop two-way shape memory strain of 1.6% without an intense training process. Transmission electron microscopy (TEM) revealed that the internal twins formed in the martensite variants were 〈0 1 1〉 type II twins