VOLUME FRACTION MEASUREMENT OF DISPERSOIDS IN A THIN FOIL BY PARALLELENERGY-LOSS SPECTROSCOPY - DEVELOPMENT AND ASSESSMENT OF THE TECHNIQUE

A method to determine the volume fraction of a dispersoid phase based on measurements carried out on thin foils is presented. The method inv olves the reconstruction of the shape and volume, by electron energy-l oss spectroscopy thickness measurements, of the analysed foil and the determination of the Volume of the dispersoids using more conventional electron microscopy imaging techniques. Hence the technique does not require the use of stereology theorems. The procedure to measure the t otal inelastic mean free path and the linearity of its measurement for thicknesses (t) relative to the mean free path (t/lambda) up to t/lam bda approximate to 4 is described, A method allowing the conversion of one single experimental lambda-value to Various collection conditions either graphically or by parameterization is also outlined. Various i maging methods (CTEM, STEM and chemical mapping) were evaluated for th eir ability to retrieve the distribution of dispersoids and thus their volume, Artefacts of the technique and of the sample preparation meth od are also discussed, The possibility of applying such techniques usi ng in-column and post-column imaging filters and the limitations of su ch methods are presented. Although the system has been applied to a re levant metallurgical system in the aluminium industry, it can be used for any other material provided that the values of the mean free path can be obtained.