Metallurgical Transactions A

, Volume 9, Issue 10, pp 1449–1460

Electron microscopy of crystalline and amorphous Ni-P electrodeposited films: In-situ crystallization of an amorphous solid

  • E. Vafaei-Makhsoos
  • Edwin L. Thomas
  • Louis E. Toth
Transformations

DOI: 10.1007/BF02661817

Cite this article as:
Vafaei-Makhsoos, E., Thomas, E.L. & Toth, L.E. MTA (1978) 9: 1449. doi:10.1007/BF02661817

Abstract

Electron microscopy has been used to study the structure of Ni-P electrodeposited thin films with 7, 12, 20 and 22 at. pct P. For the crystalline as-deposited films with 7 and 12 at. pct P (low P films), the crystal structure is fcc and the grains are a supersaturated solid solution of P in Ni. Grain size decreases with increasing P content; the present findings agree with previous ones. For “amorphous” as-deposited films with 20 and 22 at. pet P (high P content films) the amorphous phase is not completely homogeneous and there are regions in which small microcrystals exist. Electron beam heating a low P con-tent film causes the crystalline array of supersaturated Ni grains to decompose to an equilibrium mixture of Ni and Ni3P; both types of grains are randomly oriented. Electron beam heating a high P content film causes the amorphous regions to undergo several complex transformations. The first reaction to occur is: Amorphous (Ni-P) -NixPy + Ni (random) where NixPy is a newly discovered phase with a variable composition. Further beam heating causes a second transformation to equilibrium phases: NixPy + Ni → Ni3P + Ni (random). The microstructure resulting from the above transformations depends on variations in composition of the as-deposited specimens, rates of heating and temperature gradients. The mode of phase transformation in microcrystalline regions and amorphous regions is distinctly different. Crystallization in amorphous regions occurs by a nucleation and growth of NixPy, and Ni; a crystallization front is seen to advance into the amorphous re-gion. Crystallization in microcrystalline regions occurs by nucleation and growth of the Ni3P phase and grain coarsening of the Ni phase. No distinct crystallization front is ob-served.

Copyright information

© American Society for Metals and the Metallurgical Society of AIME 1978

Authors and Affiliations

  • E. Vafaei-Makhsoos
    • 1
  • Edwin L. Thomas
    • 3
  • Louis E. Toth
    • 2
  1. 1.Department of Chemical Engineering and Materials ScienceUniversity of MinnesotaMinneapolis
  2. 2.Department Chemical Engineering and Materials ScienceUniversity of MinnesotaMinneapolis
  3. 3.Department of Polymer Science & EngineeringUniversity of MassachusettsAmherst