Formation of Submicron Metastable Phase Structures in Alloys with Focused Electron or Proton Beams


Recent theoretical and experimental studies of radiation-induced segregation in alloys under irradiation with focused charged-particle beams have shown that point-defect currents generated by axial and radial displacement-rate gradients can cause significant redistribution of the alloying elements within the irradiated zone. In the case of irradiation of thin films with highly-focused electron beams, two important features have been established experimentally: (i) the diameter of the local region in which the alloy composition and phase are modified is practically equal to the beam diameter, and (ii) the time required to produce a given change in the alloy composition in the center of the irradiated zone decreases rapidly with beam diameter. Our theoretical modeling indicates that these features will also be observed in semi-infinite alloys bombarded with focused proton beams. However, in this case, the spatially-nonuniform defect production in both the axial and radial directions renders the compositional redistribution more complex. The present work shows that the ability to locally modify the alloy composition by focused electron or proton beams may offer a new method for producing local regions of controlled composition and microstructure on a submicron scale. The results of our model calculations and experimental studies will be presented to demonstrate the feasibility of this novel technique.

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Work supported by the U. S. Department of Energy, BES-Materials Sciences and BES-Applied Mathematical Sciences, under Contract W-31-109-Eng-38.

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Lam, N.Q., Okamoto, P.R. & Leaf, G.K. Formation of Submicron Metastable Phase Structures in Alloys with Focused Electron or Proton Beams. MRS Online Proceedings Library 74, 523 (1986).

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