한국주조공학회

Microstructures and shape memory characteristics of Ti50Ni20Cu30 alloy strips fabricated by arc melt overflow have been investigated by means of XRD, optical microscopy and DSC. The microstructure of as-cast strips exhibited columnar grains normal to the strip surface. X-ray diffraction analysis showed that one-step martensitic transformation of B2-B19 occurred in the alloy strips. According to the DSC analysis, it was known that the martensitic transformation temperature (Ms) of B2→ B19 in Ti50Ni20Cu30 strip is 57oC. During thermal cyclic deformation with the applied stress of 60 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be 3.7oC and 1.6%, respectively. The as-cast strip of Ti50Ni20Cu30 alloy also showed a superelasticity and its stress hysteresis was as small as 14 MPa. These mechanical properties and shape memory characteristics of the alloy strips were ascribed to B2- B19 transformation and the controlled microstructures produced by rapid solidification of the arc melt overflow process.

Shape memory alloy, Ti Ni Cu alloy, Martensitic transformation, Superelasticity, Transformation hysteresis.