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Ni-Al Intermetallics Obtained By Cold-Rolling Elemental Metal Sheets
Published October 05, 1994 by Associazione Tecnica Dell'Automobile in Italy
Intermetallics based on NiAl have attractive properties for high temperature applications as potential substitutes for superalloys, e.g., in parts for the aerospace industry. However, before reaching the application stage, there is still need for improvement of properties such as low temperature ductility and creep resistance which can be obtained through novel preparation techniques. In this respect, we present here for the first time a reaction between Ni and Al in equiatomic amounts promoted by cold rolling.
Reactions between metallic elements of high chemical affinity can occur in the solid state if proper mechanical treatment is performed to initiate interdiffusion processes (e.g., by ball milling of powders). Alternatively, the solid state reaction can be promoted by rolling together foils of the elements.
Foils of the elements were repeatedly rolled producing a multilayered structure. The elements are intimately intermixed to crystallite size of the order of a few nanometers. When the composite was heated at around 200°C a reaction occurs with formation of NiAl3. Further heating at 450°C brings about the formation of NiAl. The process is followed by DSC and XRD. The final product consists of flakes of intermetallic compound with no particles of the elements still detectable.