PHASE-FORMATION IN THE DIFFUSION COUPLE O F ALUMINUM THIN-FILM AND GOLD BULK AND THE INFLUENCE OF CALCIUM ON THE PHASE-FORMATION

The behavior of phase layer growth in the diffusion couple of aluminum thin films and gold bulks at the temperatures from 523 K to 773 K was studied by means of SEM, EPMA and optical microscopy. The effect of c alcium addition on phase layer growth was also studied. The experiment al results show: before the disappearance of aluminum thin films, five intermetallic phases in its equilibrium phase diagram form in the cou ple and after the aluminum disappearance, the phases with a lesser gol d content disappear in sequences. After the disappearance of the AuAl2 , AuAl and Au2Al phases, the Au4Al phase grows in the Au5Al2. Kirkenda ll voids are found to form in the Au5Al2, adjacent to Au4Al. The addit ion of a small amount of calcium to the Au bulks affects the morpoholo gy, making void sizes smaller and diffusion easier, thus promoting the growth of the Au4Al phase.