Microstructural Developments During Implantation of Metals
- PDF / 3,637,782 Bytes
- 10 Pages / 417.6 x 639 pts Page_size
- 105 Downloads / 212 Views
MICROSTRUCTURAL DEVELOPMENTS DURING IMPLANTATION OF METALS D. I. POTTER, M. AHMED, AND S. LAMOND Metallurgy Department and Institute of Materials Science University of Connecticut, Storrs, CT 06268 ABSTRACT The chemical and microstructural changes caused by the direct implantation of solutes ito metals are examined. The particular case involving Al -ion implantation into nickel is treated in detail. Chemical composition profiles measured using Auger spectroscopy and Rutherford backscattering, and average near-surface chemical composition measured using an analytical electron microscope, are compared with model calculations. The microstructures that develop during implantation are investigated using transmission electron microscopy. For low fluences implanted near room temperature, these microstructures contain dislocations and dislocation loops. Dislocation loops, dislocations, and voids result from implantations at temperatures near 500eC. Higher fluences at these elevated temperatures produce precipitates when the composition of implanted solute lies in a two-phase region of the phase diagram. Implanted concentrations corresponding to intermetallic compounds produce continuous layers of these compounds. Room temperature, as compared to elevated temperature, implantation may produce the same phases at the appropriate concentrations, e.g. W'-NiAl, or different phases, depending on the relative stability of the phases involved. INTRODUCTION Ion implantation provides a unique method for altering the near-surface chemical composition and microstructure of materials, and thus for improving surface sensitive properties like corrosion, oxidation, and wear resistance [1,2]. These two aspects of implantation, alteration of chemical composition and microstructure, are examined in this paper, using aluminum implantation of nickel as a representative system. First, the main factors governing the concentration profiles of implanted species are presented. It is shown that the profiles calculated on the basis of these factors agree well with those measured experimentally for the system. Second, the microstructural developments in the implantation environment are described, and the phases observed in these microstructures are compared to those expected according to the equilibrium phase diagram. Aluminum was chosen as the implanting ion because this element can be implanted into nickel to high concentrations, 575 at.ZAl in Ni. Further, the combination of aluminum and nickel is found in many so-called "superalloys", used for high-temperature turbine materials, and thus there is considerable applied interest in the Ni-Al system. Lastly, the usefulness of these alloys has resulted in a well-established data base describing their behavior under various conditions, e.g. the Ni-Al phase diagram [31, and this simplifies the interpretation of the implanted microstructures.
Mat. Res. Soc.
Symp. Proc. Vol.
27 (1984)
sElsevier Science Publishing Co.,
Inc.
118
EXPERIMENTAL PROCEDURES The implantations were performed using an analyzed
Data Loading...
