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 sa mples were analysed by in situ Rutherford backscattering/channeling sp ectrometry (RBS) and transmission electron microscopy (TEM). Samples i mplanted with lead have microstructures consisting of dense distributi ons of nanosized lead inclusions with fcc structure growing in topotac tical alignment with the matrix in a cube/cube orientation relationshi p. Single crystals implanted with lead therefore show channeling in th e lead inclusions in step with channeling in the aluminium matrix both in the [110] and the [111] directions. Channeling in the lead inclusi ons is most significant for samples implanted at higher temperatures w here the inclusions are the largest. Conversely, channeling in thalliu m inclusions from samples implanted above 525 K is only moderate in th e [110] direction and nearly absent in the [111] direction. The thalli um inclusions formed in samples implanted at temperatures up to around 450 K are a few nm in size and have a metastable fcc structure determ ined by the aluminium matrix. Their channeling properties are comparab le to that of the lead inclusions. However, at higher implantation tem peratures the size of the inclusions grow markedly, and it is no longe r possible to sustain the metastable fcc structure. Instead the inclus ions have fcc structure with a variety of orientational variants respo nsible for the changes in the channeling properties.