Atomic Diffusion Of Al And Si In Cu-base Bulk Metallic Glasses

In this dissertation, the diffusion of Al and Si in the amorphous and thesupercooled liquid state of the Cu-based (Cu_44.25Ag_14.75Zr₃₆Ti₅) bulk metallic glassforming systems with the better glass-forming ability （GFA） so far, has beensystematically investigated by X-ray diffraction （XRD）, scanning electron microscopy（SEM）, thermal analysis （DSC） and secondary ion mass spectroscopy （SIMS） andstage equipment.Cu_44.25Ag_14.75Zr₃₆Ti₅round rod object of the bulk amorphous alloy with adiameter of3mm were made in blow castiing of copper.Then it was cut for a roundflake specimens with a height of1mm through the diamond. The temperature mustbelow the glass transition temperature （Tg=623K） to ensure the amorphous alloysample was not crystallized. Though a series of experiments to reasonable choice ofamorphous alloy diffusion annealing temperature and heat preservation time.Afterthat they are still amorphous XRD detection.We only chose four temperatures andtime， they were573K（80min）、603K（60min）、633K（40min） and663K（20min）.Al and Si atoms in Cu_44.25Ag_14.75Zr₃₆Ti₅bulk metallic glass and alloys diffus inthe distance by stripping step by step way of testing through the using of secondaryion mass spectromety （SIMS） and the becel meter. They were found that Al and Siatoms in the supercoold liquid region between the diffusion coefficient andtemperatures are in line with the same Arrhenius relationship. The unique diffusioncoefficient and diffusion activation energy show that the diffusion mechanism ofsilicon is unique in the experiment temperature range，the autom group diffusiontogether is orssible.But the Al and Si atoms in alloys diffusion primarily by speaceand grain boundary.By Fick’s law the average diffusion activation energy of Al and Si werecalculated, they were1.82×10⁵J/mol and7.92×10⁴J/mol.Although Al and Si atomsradius are not significant, but the diffusion distance in amorphous alloy and alloys aregreater than the Al atoms. Because Si atom is non-metallic element, it is very strong inthe substrate metal atoms so that the diffusion distance became much greater.