We are interested in the spatial resolution of the role of Si on different phase formations of the Al-Fe-Si and Al-Fe-Mn-Si system within the intermetallic seam of Al-Fe welds.
(a) Focussed ion beam (FIB) amella prepared from a Si-containing filler material within an Fe-Al weld, and (b) transission-electron-microscopy and energy dispersive X-ray spectrometric (TEM-EDS) chemical profiles and (c,d) TEM-EDS maps reveal the inhomogeneous distribution of Fe and Si within the intermetallic Al-Fe „η phase“. (e) Selected area diffraction (SAED) patterns of short-range ordered (yellow box) and long-range ordered (LRO, green box) regions within the η grain. We show that locally decreased Si content corresponds with the formation of long-range order within the grain. This is confirmed by superstructure reflexes (blue arrow), The ordering state has been identified as the „η’’’ phase“. In the region of high Si contents (yellow circle/box), diffuse scattering (white arrows) indicates a lack of such type of long-range order.