Microstructure of rapidly solidified Cu-Al-Ni shape memory alloy ribbonsLojen, Gorazd (Avtor) Anžel, Ivan (Avtor) Kneissl, Albert C. (Avtor) Unterweger, Elfride (Avtor) Kosec, Borut (Avtor) Bizjak, Milan (Avtor) metallurgyshape memory alloysCu-Al-Ni alloymicrostructuremelt spinningCu-Al-Ni shape memory alloys (SMAs) are currently the only available high temperature SMAs, showing a good resistance against functional fatigue. In polycrystalline state, they are very brittle and exhibit, in general, only small reversible deformations. By melt spinning, thin Cu-Al-Ni ribbons can be manufactured directly from the melt. Appropriate casting parameters can ensurea single layer columnar structure with a fibre texture, which significantly increases the maximal reversible strain in longitudinal direction. Cu-Al-Ni ribbons, containing 13, 14 and 15 wt.% Al were cast by free jet melt spinning. Because of the alloys' low thermal conductivity, the cooling rate was surprisingly low - considering the crystal grain size - significantly below 103 K/s. Therefore, wide ribbons having a single layer columnar and (except the ribbons containing 13 wt.% Al) completely martensiticstructure could not be obtained. Regardless the chemical composition, the ribbons have a single layer columnar structure only if the thickness does not exceed approximately 50 m, otherwise the structure consists of at least two layers of equiaxed grains. In as-cast condition, only ribbons containing 13 wt.% Al seem to be completely martensitic. Heat treatments at temperatures up to 900 °C improved the structure of 13 and 14 wt.% Al ribbons. All ribbons exhibit one-way shape memory effect in as-cast condition. Heat-treated ribbons containing 13 wt.% Al exhibited two-way shape memory effect already after one bending and heating cycle.20052012-06-01 09:39:13Neznano27025UDK: 669.018COBISS_ID: 9607190ISSN pri članku: 0924-0136NUK URN: URN:SI:UM:DK:SXUPLTDVsl