Internal stress measurements by convergent beam electron diffraction on creep-deformed Al single crystals

Convergent beam electron diffraction (CBED) was performed on aluminum single crystals that were creep deformed within the five-power-law regime. Well defined subgrains were formed with a Frank network of dislocations within the subgrains. The objective of this work was to probe the subgrains from one subgrain boundary to another using CBED. This allowed a determination of any changes in the lattice parameter, which would indicate the presence of any internal stresses. Earlier investigations by others suggested that internal stresses may be high in the vicinity of the ‘hard’ subgrain boundaries based on a variety of techniques, including X-ray diffraction, stress-dip tests as well as some preliminary CBED. It was determined in this work that the lattice parameter was unchanged at the equilibrium or stress-free value within the interior of the subgrains and along (within one beam diameter) the subgrain boundaries.