Ferromagnetic shape Memory of Nanostructure Fe-Pd Alloy: The Texture Observation Study by Laser and Electronic Microscopes.

摘要

Ferromagnetic shape memory Fe-29.6at%Pd alloy ribbon (about 60 micrometer thickness) prepared by the rapid solidification melt-spinning method has a large magnetostriction of 1.0 x 10(exp -3) when a magnetic field of 10 kOe is applied normal to the ribbon surface at room temperature. The strain induced by magnetic field is caused by the conversion of variants in the martensite phase and increases with temperature and has a maximum at phase transformation temperature of 380-400 K. However, the mechanically shape recovery effect of the ribbon has two-step phase transformation temperature of 300-330 K and 380-420 K. To investigate the origin, we observed the texture by using laser microscope and high resolution electronic microscope. The cross section of ribbon shows columnar structure of about 10 micrometers in width. The ribbon consists of three parts: both upper and bottom surfaces have small grains of 2-3 micrometers with strong 100 texture and the inner part has fine layer-structures of 30-40 nm thickness in grains. It can be concluded that this nano-scale composite structure makes phase transformation temperature increase from 300 K in surface to 380-400 K in inner part.