The characterization of iron aluminide green sheet thermal properties

The first step in the fabrication of a thin FeAl sheet from metal powder is the formation of a green sheet, by either cold rolling or tape casting a mixture of 60 μm FeAl particles and organic binding agents. The green sheet composite is approx. 700 μm thick with a bulk density which is approx. 3.6 g/cm3. The composite then undergoes a series of process steps (binder elimination, densification, sintering, annealing) to form the final FeAl sheet product which is approx. 200 μm thick with a density of approx. 6.0 g/cm3. Non-uniformities within the green sheet have been found to be a major contributor to material failure in subsequent sheet processing, forming and cutting. This paper describes a non-contact and non-destructive method for inspecting iron aluminide green sheet material during processing. This thermographic inspection technique takes advantage of the differences in heat flow arising from the variations in mass distribution and sheet thickness, as well as green sheet constituents, voids and cracks. The ability to detect and correct variations during green sheet formation has the potential to significantly improve the quality of the final product.