Investigation of the two martensitic phase transitions hcp- dhcp and dhcp- fcc in Co-0.85at%Fe by neutron scattering

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 1999-12, Vol.273, p.491-493
• Main Authors: Prem, M., Krexner, G., Blaschko, O.
• Format: Article
• Language: English
• Subjects: Co based alloy; Double-hexagonal phase dhcp; Martensitic transformation; Neutron scattering; Phonons
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/S0921-5093(99)00385-8

Upon heating, Co-0.85at%Fe undergoes the two martensitic phase transitions hcp→ dhcp (at ∼590 K) and dhcp→ fcc (at ∼690K). The transitions are characterized by a large hysteresis permitting to investigate properties of two phases at the same temperature, respectively. The distance between neighboring close-packed planes remains virtually constant during the hcp- dhcp transition while a change of ∼0.3% is observed at the dhcp- fcc transformation. The lattice dynamics of Co-0.85at%Fe was investigated by means of inelastic neutron scattering at a series of temperatures up to 750 K in order to look for precursor effects in the phonon dispersion curves near the two martensitic transformations. In all of the phonon branches investigated, anomalies were neither found near the hcp- dhcp nor the dhcp- fcc transition. Both transformations in this system occur slowly and with a continuous change of the volume fractions of the phases involved over periods of several hours.