Microstructural analysis of a FeAl/quasicrystal-based composite prepared using a focused ion beam miller

A composite consisting of a brittle multiphase matrix containing bath an Al -based quasicrystalline phase (psi) and an ordered body centred cubic phase (beta) and a relatively ductile ordered body centred cubic intermetallic F eAl phase has been developed as an abrasive wear-resistant coating material . It is applied as a 500 mum thick layer onto stainless steel substrates th rough plasma spray processing. The microstructure of such materials can be readily examined by optical and scanning electron microscopy, but the inher ent difficulty of preparing transmission electron microscope (TEM) samples has inhibited higher resolution studies. However, the relatively recent dev elopment of the focused ion beam (FIB) miller as a tool in materials scienc e provides a method ideal for the preparation of TEM specimens of these mat erials. In this study a coating consisting of a mixture of an Al-Cu-Fe base d quasicrystal and FeAl+Cr was deposited on to a 304 stainless steel substr ate, TEM specimens were prepared using a FIB and subjected to detailed micr ostructural characterization. The structure consisted of elongated bands of a FeAl phase about 100 nm in width and several micrometres in length, whic h enclosed more equiaxed regions about 1 mum in diameter that consisted of fine mixtures of quasicrystal and two Al-Fe-Cu phases isostructurally relat ed to FeAl.