HIGH-RESOLUTION TRANSMISSION ELECTRON-MICROSCOPY STUDIES OF THE MICROSTRUCTURE OF NANOCRYSTALLINE TI70NI20SI10 ALLOY

The microstructure of nanocrystalline Ti70Ni20Si10 alloy with various grain sizes was investigated by high resolution transmission electron microscopy (HRTEM). The nanocrystalline samples were prepared by annea ling the amorphous precursor. At an initial stage of annealing, homoge neous nucleation of Ti2Ni stable crystalline phase was found to occur. In the later stage, Ti5Si3 and a small amount of alpha-Ti were found to coexist. Based on the HRTEM observations, most of the grain boundar ies have ordered structures and no obvious disordered regions were det ected at the grain boundaries. However, asymmetric tilt grain boundari es were often encountered The samples are essentially free from any po rosity. No signs of lattice defects, such as twins, stacking faults or dislocations were found to be present inside the grains.