J. Phys. IV France 07 (1997) C5-167-C5-172
Martensitic Transformation in CuAlMn and CuAlNi Melt Spun RibbonsJ. Dutkiewicz1, J. Morgiel1, T. Czeppe1 and E. Cesari2
1 Institute of Metallurgy and Materials Science of the Polish Academy of Sciences, ul. Reymonta 25, 30-059 Kraków, Poland
2 Physics Department, University of Balearic Islands, Cra de Valldemossa km7.5, 07071 Palma de Mallorca, Spain
The martensitic transformation was studied in CuAlMn and CuAlNi alloys transforming at elevated temperatures i.e. 70 - 250 °C. All alloys possessed mixed 18R and 2H structure of martensite. Splat quenching caused a direct formation of martensite and a considerable decrease of the grain size from about 100 µm in the bulk (in spite of TiB additions) down to about 2 µm. The martensite was less prone to stabilization as in bulk water quenched alloys. The DO3 domains size was not altered in ribbons due to insufficient cooling in the solid state after casting. Their size was considerably lowered in ribbons cooled directly in water after casting. Martensitic transformation temperatures were shifted to lower temperatures by 20 - 50 °C, but the transformation hysteresis was 10 - 20 °C broader in all alloys investigated. Transmission electron microscope (TEM) in-situ heating/cooling experiments allowed one to follow the nucleation of martensite in splat quenched ribbons due to their fine grain size. It appeared that martensite needles nucleated at the grain boundaries. Growing needles, approaching grain boundaries induce formation of other plates at adjacent grains.
© EDP Sciences 1997