In order to study the initial mechanism of sintering of an alloy, a few spherical beads of 30-70 Au-Ag alloy (which is prealloyed) are hot-pressed and sintered by the same method as described in the former report
1)2). The diameters of beads tested are 1.35, 0.85 and 0.45 mm. Forlexample, the beads (0.85mm in dia.) are sintered at 453°K for 5 minutes under a load of 3.5 kg or at 1193°K for 5 minutes under no load. These temperatures are 35 and 94% of the melting point of this alloy respectively. ectivel The value of _??_where
W is the load, 2
r the diameter of bead and
t the sintering time, changes with the lowest sintering temperature
Ts. In the case of 0.85 mm in diamter, ξ has a maximum value in the range of recrystallization temperature of this alloy (200°_??_500°C).
The ratio of the diameter of adhered area between two beads to the diameter of the bead is found to take a certain value independent of the dimension of the bead, but it becomes larger with the load. For example, it is about 5.5% under no load, but about 18% under a load of 100g.
The activation energy to effect sintering between two beads changes with the lowest sintering temperature. In the case of 0.85 mm in diameter, it becomes smaller with the lowest sintering temperature, but has a minimum value within the range of recrystallization temperature and then it becomes larger. Its minimum value is about 23 kcal/mol and the largest value is 73 kcal/mol., These values are respectively about 1/2 and 6.5 times as large as the activation energies of self-diffusion of gold (44.1 kcal/mol) and silver (44.7 kcal/mol) in 50-50 Au-Ag alloy
4).
抄録全体を表示