Growth kinetics of gamma 2 crystals on mercury-plated Ag3Sn.

Previous work has shown that needles of gamma 2 crystals form when mercury is plated on the surface of an Ag3Sn specimen. In the present study, the growth kinetics of gamma 2 needles were investigated from room temperature to 50 degrees C for varying amounts of plated mercury. Straight-line relationships between crystal length and the square root of the time of growth showed that the growth rate is diffusion controlled. The growth rate increased with temperature up to 40 degrees C but decreased at higher temperatures. Further, as the temperature was increased, fewer gamma 2 crystals formed and their growth length decreased. This demonstrates that a number of competing factors are involved in the growth process at high temperatures.