On the application of energy filtering TEM in materials science .2. Study of a fibre-reinforced metal matrix composite

Energy filtering TEM (EFTEM) studies of a fibre-reinforced Ti-6Al-4V alloy designed for use in high temperature aerospace applications have been performed using a Philips CM20 TEM equipped with a Gatan imaging filter. The fibre employs a developmental duplex coating based upon a compliant layer of gadolinium metal and a gadolinium boride reaction layer both deposited by physical vapour deposition. EFTEM elemental maps, employing a background subtraction procedure, as well as the more simple jump-ratio images were recorded using the Si L(23)-, Gd N-45-, B K-, C K-, Ti L(23)-, O K-, Gd M(45)-edges and a comparison between the two methods is presented. Important information on inhomogeneities in the deposited layers, reactions occurring at the coating-fibre and coating-matrix interfaces and the nature of the diffusion processes was derived from these results. In order to support the interpretation of the EFTEM element distributions, electron energy-loss spectra (EELS) have been recorded on regions of interest and subsequently quantified to yield the composition of the phases. This investigation highlights the benefit of combining EELS and EFTEM in the characterization of complex microstructures. Copyright (C) 1996 Elsevier Science Ltd.