Metallurgical and Materials Transactions B

, Volume 3, Issue 11, pp 2757–2767 | Cite as

The genesis of the cellular precipitation reaction

  • R. A. Fournelle
  • J. B. Clark
Symposium on the Cellular and Pearlite Reactions


The morphology of cellular precipitation in a Cu-9.5 at. pet In alloy has been investigated by light and electron microscopy. Both cellular and general precipitation were observed to occur simultaneously in quenched and aged alloys while only cellular precipitation was observed to occur in isothermally aged alloys. Because of the presence of wide, solute rich, precipitate free zones in the vicinity of grain boundaries in the quenched and aged alloys, the early development of cellular precipitation was found to be identical for both types of heat treatment. From light and electron microscopy observations of the early stages of cellular precipitation a mechanism for the formation of cells was developed. At the start of aging, the unoccupied grain boundary begins to migrate under the influence of grain boundary migration forces as if it were in a single phase alloy. As the boundary migrates, solute segregates along it to form allotriomorphs which pin the boundary. The boundary continues to migrate and bows between the simultaneously forming allotriomorphs. With further aging, the allotriomorphs lengthen following the bowing boundary and the allotriomorphs become the initial precipitate lamellae of the developing cell as a steady-state lamellar structure develops. Assuming that the critical step in the development of a cell is the ability of the boundary to bow between the initial allotriomorphs, a criterion for the occurrence of cellular precipitation was developed.


Metallurgical Transaction Aging Temperature Aged Alloy Boundary Migration Precipitate Free Zone 
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Copyright information

© The Metallurgical of Society of AIME 1972

Authors and Affiliations

  • R. A. Fournelle
    • 1
  • J. B. Clark
    • 2
  1. 1.Department of Mechanical EngineeringMarquette UniversityMilwaukee
  2. 2.Metallurgical EngineeringUniversity of Missouri-RollaRolla

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