Kinetics and Grain Boundary Selectivity of Discontinuous Precipitation in Binary Ni-Cr Alloy

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 48; no. 6; pp. 3096 - 3107
• Main Authors: Keskar, N., Pattanaik, A. K., Mani Krishna, K. V., Srivastava, D., Dey, G. K.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-06-2017; Springer Nature B.V
• Subjects: Aging; Alloys; Cameras; Characterization and Evaluation of Materials; Chemistry and Materials Science; Discontinuity; Gas turbine engines; Grain boundaries; Grain boundary migration; Materials Science; Metallic Materials; Metallurgy; Microstructure; Nanotechnology; Nickel base alloys; Nucleation; Oxidation; Physical metallurgy; Precipitation hardening; Structural Materials; Surfaces and Interfaces; Temperature; Thin Films; Incoherent Interface; Reaction Front; Interlamellar Region; Continuous Precipitation; Discontinuous Precipitation
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-017-4066-1

A supersaturated Ni-Cr alloy (42 wt pct Cr) was subjected to a series of aging heat treatments in the two-phase region in the temperature range of 923 K to 1123 K (650 °C to 850 °C) for different time periods. The resultant microstructures were seen to be composed of varying volume fractions of continuous (CP) and discontinuous precipitation (DP). The DP dominated at lower temperatures, while CP dominated at higher temperatures and the expected DP termination temperature was estimated to be 1138 K (865 °C). The kinetics of DP followed the Turnbull model at lower temperatures and the Aaronson–Liu model at higher temperatures. The nucleation and growth of DP cells, which occurred
via
the ‘precipitate driven grain boundary migration,’ was seen to be a strong function of the nature of the participating grain boundaries.