Martensitic transformation in Ni–Ti–Co strip produced by twin roll casting

✍ Scribed by T. Goryczka

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 269 KB
• Volume: 481-482
• Category: Article
• ISSN: 0921-5093
• DOI: 10.1016/j.msea.2007.03.116

✦ Synopsis

The process of the martensitic transformation was studied in a Ni 47 Ti 50 Co 3 shape memory alloy produced by twin roll casting. Differential scanning calorimetry, X-ray diffraction and electron microscopy were used. The as-cast strip reveals a multi-step martensitic transformation. It proceeds from the parent phase through the R-phase after which two stages of the B19 martensite transformation are observed. Stabilization of the martensite was obtained directly after several thermal cycles carried out in a relatively low thermal range (-100 to 70 • C), without the commonly used annealing (350-700 • C). The thermal cycling leads to a single stage of the B19 martensitic transformation, however, the transformation enthalpy of the R → B19 transition does not change. The alloy transformation behavior was compared with that observed in a cycled melt-spun ribbon. The energy stored in the twin roll cast strip is higher than that stored in the melt-spun ribbon.