Ordering of the β phase in TiNiCu and TiNiCuMn melt spun ribbons studied with the ALCHEMI technique

Ti–25Ni–25Cu and Ti–25Ni–23Cu–2Mn (at.%) ribbons were melt spun at 26 m s−1. Transmission electron microscopy (TEM) investigations proved that the Mn addition lowers the amount and reduces the size of the β phase crystallites present in the otherwise amorphous matrix. The observations using the (1 0 0) superlattice spot proved that each crystallite forms a single antiphase domain. The planar ALCHEMI experiments at (0 0 0, 1 0 0) orientation of thin foils from as-spun ribbons confirmed a high occupancy of the Ni-rich planes by Cu and Mn additions. However, even as practically all Mn atoms found their places on the Ni-rich planes, though a small amount of Cu atoms still occupy the planes characteristic for Ti atoms. The transfer of the remaining Cu atoms from Ti {1 0 0} to Ni {1 0 0} planes might be the reason of the rise of the temperature of the start of the martensite transformation (Ms) during further heat treatment.