Quantitative Transmission Electron Microscopy of Bubbles in A1 and A1-A12O3 Alloys

Abstract

The density and size distribution of small helium bubbles, present in thin foils of A1 and A1-A12 O3 after alpha particle bombardment and postbombardment annealing, were measured by means of transmission electron microscopy. For making these measurements the conditions for visibility were first established by theoretical calculations of contrast for void sizes similar to those of the observed bubbles. Micrographs were then taken in suitable contrast conditions and the number and size of the bubbles measured on the micrographs. It was found that the density of small bubbles, present in the matrix, can be measured accurately. The density of small bubbles attached to particles, on the other hand, is difficult to measure. Furthermore, the size of very small bubbles is hard to determine with precision since it depends on different parameters. The size and shape of larger bubbles can be established by tilting and stereomicroscopy.