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Effect of Heat Treatment on the Ductility of Ni(γ)/Ni3Al(γ') Two-phase Alloy Foils

Published online by Cambridge University Press:  26 February 2011

Motonori Nakamura
Affiliation:
[email protected], University of Tsukuba, Graduate School of Pure and Applied Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 3050047, Japan
Masahiko Demura
Affiliation:
[email protected], National Institute for Materials Science, Fuel Cell Materials Center, 1-2-1 Sengen, Tsukuba, Ibaraki, 3050047, Japan
Ya Xu
Affiliation:
[email protected], National Institute for Materials Science, Fuel Cell Materials Center, 1-2-1 Sengen, Tsukuba, Ibaraki, 3050047, Japan
Toshiyuki Hirano
Affiliation:
[email protected], National Institute for Materials Science, Fuel Cell Materials Center, 1-2-1 Sengen, Tsukuba, Ibaraki, 3050047, Japan
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Abstract

The microstructures and room-temperature tensile properties were examined in the 95% cold-rolled and subsequently heat-treated foils of the boron-free Ni(γ)/Ni3Al(γ') two-phase (Ni-18at.%Al) alloys. The electron backscatter diffraction measurements revealed that the recrystallization started at 873 K/0.5 h and that it completed at 1273 K/0.5 h. While the foils showed no tensile elongation in the cold-rolled state, they became ductile after the heat-treatments at 873 K and above. The tensile elongation increased with the increasing heat-treatment temperature: it reached to 14% at 1273 K/0.5 h. The tensile elongation and the fracture strength were high, compared to those in the γ' single-phase foils. The fracture mode was intergranular, and it changed to a mix of intergranular and transgranular in the foils heat-treated at 1273 K/0.5 h, where the area fraction of crack resistant boundaries such as °1, °3 and °9 was high, 0.63. The high ductility was ascribed to the existence of the ductile γ matrix and to the high fraction of crack-resistant boundaries.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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