Shape memory properties of Cu-based thin wires obtained by the "in rotating water spinning" technique

Abstract
Cu-Al-Ni-based cylindrical wires with diameters ranging between 100 and 250 m have been successfully produced directly from the melt using the "In Rotating Water Melt-Spinning" (INROWASP) technique. In such a method, a cylindrical jet of molten alloy is ejected into a liquid cooling layer (water) disposed in the inner surface of a rotating drum. This soft cooling medium allows to preserve the cylindrical shape after solidification. Due to the rapid solidification, the martensitic transformation temperatures of the as-prepared wires are depressed in relation to the bulk alloy. Ageing at moderate temperatures (250°C) increases the transformation temperatures of the wires and of the same alloys in bulk form. However, the decrement in the transformation temperatures of the wires still persists, due to their finer grain size. They exhibit superelasticity as well as shape memory properties, both for uniaxial elongation and bending. When biased by a constant aniaxial tensile stress, an elongation up to 2% (at ~ 70 MPa) is attained, in the as-prepared form, upon cooling down the transformation, completely recovered on heating. The recoverable elongation decreases to 1.2% for wires aged 700 h at 520K.