IN-SITU OBSERVATIONS OF R-PHASE TRANSFORMATION IN A TI50NI48FE2 ALLOYBY ELECTRON-MICROSCOPY

The R-phase transformation In a Ti50Ni48Fe2 alloy was studied by in-si tu electron microscopy with double-tilt cooling stages and an energy-f ilter, and the controversial Incommensurability in the early stage of the transformation was examined by using imaging plates, which have hi gh sensitivity and are easy to access to computer analysis. As a resul t, the transformation was shown to proceed in the following way. The R -phase transformation starts at R-s point, where the electrical resist ance starts to increase, from the B2 parent phase with weak diffuse sc attering to the commensurate R-phase with a sharp interface. Thus, the transformation is a first order throughout, and the temperature hyste resis represents the two-phase region of the B2 parent and Ii-re comme nsurate R-phase.