Effect of quenching rates on equiatomic NiTi ribbons fabricated by melt-spinning

Quenching rates, in terms of circumferential wheel speed, in melt-spinning play an important role in the resultant characteristics of the ribbons. In this study, the effect of various wheel speeds on ribbon dimensions, cross-sectional microstructures and crystallographic texture of samples were investigated.

The Ni-50.3 at% Ti melt-spun ribbons were produced under 200 mbar He atmosphere at wheel speeds of 5 to 30 ms^-1 using a quartz crucible coated internally with Y2O3. Cooling rates during melt-spinning are directly proportional to the wheel speed and inversely proportional to the square of the ribbon thickness. Both of these parameters affected the extent of the different characteristics of the ribbons.

The microstructures of the samples were observed using scanning electron microscopy and optical microscopy, and the shape memory effect of samples was studied by differential scanning calorimetry, X-ray diffraction and tensile tests.