THE MECHANISMS OF PHASE-TRANSFORMATION IN-DIFFUSION COUPLES OF THE CU-SI SYSTEM

The mechanisms of diffusional transformation in a series of couples be longing to the CuSi system were studied. The couples consist of elemen tal materials or intermediate phases. For the Cu-Si couple it was foun d that the diffusion layer comprises the Cu3Si (eta '') phase solely. For the Cu5Si(gamma)-Si couple the diffusion zone contains the eta ''- phase subdivided into two morphologically different parts. In the Cu-e ta '' and Cu-gamma couples, formation of a narrow reaction zone with f ragmentary structure took place. Models for processes occurring in eac h of the couples during diffusional annealing were put forward. It was shown that the dual microstructure of the eta ''-phase in the gamma-S i couple can be attributed to different formation mechanisms on either side of the growing phases.