Formation of Nano-Sized Y2O3 Dispersoids in Mechanically Alloyed Ni–(Cr, Y2O3, Y) Alloys During Heat-Treatments
Abstract:In the present work, the evolution of nanoparticles during annealing and hot-consolidation in mechanically alloyed Ni–22Cr–1.5Y, Ni–22Cr–1.5Y2O3 and Ni–3% Y2O3 was examined. The highenergy ball-milling of elemental powders resulted in the complete dissolution of the constituent Cr, Y, or Y2O3, forming a Ni-based solid solution. During the subsequent annealing, however, oxide particles precipitated from the solid solution. In the case of mechanically alloyed Ni–22Cr–1.5Y2O3, over-grown Cr2O3 precipitated at a temperature as low as above ∼500 °C and ternary YCrO3 particles precipitated at 1100 °C. In the case of mechanically alloyed Ni–22Cr–1.5Y, on the other hand, the binary Y2O3 phase precipitated at 1100 °C during spark plasma sintering. The presence of Cr in the alloy composition facilitated the formation of Cr2O3 or YCrO3, and the precipitated oxides were highly prone to grain growth during hot-consolidation, sometimes reaching several micrometers. In Cr-exempt Ni–3%Y or Ni–3% Y2O3, however, the growth of nanodispersoids was restrained even at temperatures as high as 1000 °C and the resulting dispersoid was only nano-sized Y2O3.
Document Type: Research Article
Publication date: July 1, 2012
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