Papers by Keyword: Ni-Al Alloys

Abstract: The article describes the results of studies of Ni-Al ultrathin films obtained by the resistive thermal evaporation method and having the characteristic dimensions of islands of 700-1000 nm with a film thickness of about 500 nm. This paper presents a method of obtaining a film using a unit for creating high vacuum and the subsequent deposition of the film. The obtained film sample was studied using an optical microscope, a scanning probe microscope and a Fourier analyzer. The kinetic characteristics of the film, the film relief, and the characteristic dimensions of the islands were established; the search for regularities in the island structure of films was carried out and its electrical conductivity was determined.

Abstract: Nanostructured Powders of Ni-20wt%Al and Ni-50wt%Al Were Prepared, by Mechanical Alloying under an Argon Atmosphere, from Elemental Ni and Al Powders Using a Planetary Ball Mill (type Fritsch P7) for Different Times (0.5-24h).). Microstructural and Structural Features of the Final Products Were Characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). the Results of the XRD Shows the Formation of the B2 (Ni Al) Phase after 2 Hours of Milling for both Systems. Also Detected Was the Ni₃al Phase in Ni₈₀al₂₀ after 4 Hours. Crystallite Size Refinement of the Final Product Occurred down to Nanometer Scales when the Milling Time Increased, and Attained 17 Nm in the Ni₅₀al₅₀ System and 20 Nm in the other System, at 24 Hours. this Decrease in Crystallite Size Is Accompanied by an Increase in the Interval Level Strain. the Kinetics of Al Dissolution during the Milling Process of Ni₅₀al5₀ System Can Be Described by Two Regimes, Characterised by Different Values of Avrami Parameters which Are Calculated by Using the Johnson–Mehl–Avrami Formalism.

Abstract: NiAl shape memory alloy thin films have been fabricated by a solid-state reaction in Al/Ni bilayer films. Two kinds of synthesis have been used. The first one consists in heating an Al/Ni bilayer film system to temperatures above 480 K. The second one implies the successive deposition of nickel and aluminum films onto a substrate with a temperature above 480 K. Regardless of a kind of the solid-state synthesis, the films obtained reveal a two-way shape memory effect. It is supposed that the solid-state reaction in Al/Ni bilayers starts at a temperature AS of the reverse of the martensitic transition in NiAl alloy. This indicates that the NiAl shape memory alloy thin films can be formed directly during the synthesis without need for lengthy heat treatment.