STRUCTURE CHARACTERIZATION OF Sn-BASED AND Ce-BASED ALLOYS TREATED BY ULTRAFAST SCANNING

摘要

Fast scanning calorimetry (FSC) is a newly developed instrument for investigating structure evolution under non-equilibrium conditions, i.e. heating and cooling. Combined with the focused ion beam (FIB) and high resolution transmission electron microscopy (HRTEM), it is now possible to characterize the structure of the infinitesimal samples treated by ultrafast scanning rate. For Sn3.5Ag (wt.%) droplet quenched at controllable rate of 15,000 K/s, the size of intermetallics was in nanometer scale and abundant defects such as vacancies and dislocations were found. As for heating scanning, the structure of Ce_(68)Al_(10)Cu_(20)Co_2 (at.%), a kind of bulk metallic glass, heated at 5000 K/s was also detected. It was found that this rapid heating could prevent the growth of nucleus and consequently a number of nanocrystals were obtained from the amorphous matrix. Thus, attributing to the advantages of FSC, a novel approach to investigate the structure evolution of materials under extreme heating and cooling processes was developed.