Microstructural evolution and superelastic properties of ultrafine-grained NiTi-based shape memory alloy via sintering of amorphous ribbon precursor

Recent Developments in Ultrafine Shape Memory Alloys Using Amorphous Precursors

“…By hot pressing the overlapped as-cast amorphous plates, an AAP with a millimeter-scale thickness could be achieved. Cai et al [122] reported the development of an ultrafine Ni-Ti-Zr-Cu SMA using the SPS method on an AAP with a thickness of 70 µm. The grain size of the as-sintered bulk SMAs increased from 250 nm to 450 nm with an increase in the sintering temperature from 723 K to 923 K. The as-sintered bulk SMA with ultrafine grains exhibited perfect superelasticity with a high recoverable strain of ~5.8%, which is attributed to the high resistance to grain boundary slip or dislocation slip generated in the austenite matrix from the secondary phase of the residual nanoscale amorphous phase.…”

Fabrication of nickel-titanium-iron shape memory alloys by powder metallurgy route and analyses of their physical and mechanical behaviour

“…(2) In the solid state technique, the final shape is obtained by powder metallurgy route, and this technique is beneficial due to its simple procedure and low processing cost [19]. The other solid-state methods include selective laser melting [20][21][22], conventional sintering [23], microwave sintering [24], self-propagating high-temperature synthesis [25], spark plasma sintering [26] and metal injection molding [27]. The problem of the liquid state over solid processes is: (1) segregation or extensive grain growth, (2) Not fulfilling the exact composition requirements, and difficulty in manufacturing the complex shapes [28].…”