Journal of Materials Research

Table of Contents - January 2007 - Volume  22   

Articles

Metastable phase evolution in Al2O3 dispersed nanocrystalline NiCr alloys

Dheepa Srinivasana1 c1 and P.R. Subramaniana2

a1 Materials Research Lab, GE India Technology Center, EPIP Phase-2, Bangalore—560066, India

a2 Ceramic and Metallurgy Technologies, GE Global Research, Schenectady, New York 12309

Abstract

The high temperature structural stability of nanograined NiCr alloys reinforced with nanoscale yttria and alumina dispersoids, fabricated by electron beam physical vapor deposition (EBPVD), was examined. The yttria particles coarsened very little and also inhibited grain growth in the matrix successfully, whereas the alumina dispersoids coarsened rapidly and were not as effective in restricting matrix grain growth. A hierarchy of phase transformations took place in the Al2O3 particles present as nano dispersoids in a nanograined NiCr matrix S0884291400092281_inline1, on annealing. Coarsening of the alumina particles was accompanied by these phase transitions. The phase evolution is attributed to differences in free energies between the metastable and stable phases and a kinetic hierarchy in nucleation, brought about by structural and hence interfacial energy considerations.

(Received June 20 2006)

(Accepted August 24 2006)

Key Words:

  • Dispersions;
  • Nanoscale;
  • Physical vapor deposition (PVD)

Correspondence:

c1 Address all correspondence to this author. e-mail: Dheepa.srinivasan@geind.ge.com

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