The Migration of Grain Boundary on the Solid Phase Weld Interface

Abstract

A micro-cavity in a polycrystalline metal plays a role of barrier to the migration of grain boundaries. It is presumed from previous investigations that a number of micro-cavities remain along the weld interface of solid phase welds and impede the migration of grain boundaries at high temperature.
The solid phase welds in pure copper were made in 5 minutes at 400°C with about 30% deformation in thickness in high vacuum. Post-heat treatments were carried out on such welds at temperatures in the range 900-1060°C in high vacuum. The result was examined metallurgically and it was concluded that a migration of fixed grain boundaries on the weld interface occurred across the weld interface when a shrinkage or elimination of micro-cavities on the weld interface was accomplished by the volume diffusion of atoms from the grain boundaries to the micro-cavities during post-heat treatment. From this point of view the metallurgical mechanism in solid phase welding was considered.