CHANNELING AND TEM INVESTIGATION OF NANOSIZED THALLIUM INCLUSIONS IN ALUMINUM

Metastable and stable nanosized crystalline inclusions of thallium and lead have been produced in an aluminium matrix by implantation of the respective ions into pure aluminium single crystals. The implanted samples were analysed by in situ Rutherford backscattering/channeling spectrometry (RBS) and transmission electron microscopy (TEM). Samples implanted with lead have microstructures consisting of dense distributions of nanosized lead inclusions with fcc structure growing in topotactical alignment with the matrix in a cube/cube orientation relationship. Single crystals implanted with lead therefore show channeling in the lead inclusions in step with channeling in the aluminium matrix both in the [110] and the [111] directions. Channeling in the lead inclusions is most significant for samples implanted at higher temperatures where the inclusions are the largest. Conversely, channeling in thallium inclusions from samples implanted above 525 K is only moderate in the [110] direction and nearly absent in the [111] direction. The thallium inclusions formed in samples implanted at temperatures up to around 450 K are a few nm in size and have a metastable fcc structure determined by the aluminium matrix. Their channeling properties are comparable to that of the lead inclusions. However, at higher implantation temperatures the size of the inclusions grow markedly, and it is no longer possible to sustain the metastable fcc structure. Instead the inclusions have fcc structure with a variety of orientational variants responsible for the changes in the channeling properties.