ON THE NATURE OF THE APPARENT COALESCENCE OF GRAINS.

By the example of the alloy EI765 (KhN70VMOT), it is shown that the structural coarsening usually observed in metallographic analysis as the coalescence of grains with the formation of ″broken boundaries″ at early stages of the process, is actually mainly due to the formation and migration of the incoherent stepped boundaries of twins. The new twin boundaries do not have as much energy as the original high-angle ones. Coherent twin boundaries are not decorated by dispersed phases and are only revealed by special methods of etching. They are not revealed by normal methods and give the impression of ″broken boundaries″ . The process occurs when the normal migration of high-angle boundaries is delayed for some reason or other.