A TRANSMISSION ELECTRON-MICROSCOPY INVESTIGATION OF INVERSE MELTING IN NB45CR55

In inverse melting, a supersaturated crystalline phase transforms poly morphously under heat treatment to the amorphous state. Inverse meltin g of body-centered cubic (bcc) Nb45Cr55 is studied using transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The crystal line to amorphous transformation is heterogeneous, initiating at the b cc grain boundaries. HRTEM reveals 2-3 nm domains with medium range or der (MRO) in the amorphous phase. Preferred orientation of MRO domains is found on a scale corresponding to the precursor bcc grain size. Us ing HRTEM and calorimetry, MRO development in cosputtered Nb45Cr55 fil ms is characterized and compared to that in the amorphous phase produc ed by inverse melting.