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On the origin of a remarkable increase in the strength and stability of an Al rich Al-Ni eutectic alloy by Zr addition

Pandey, P. and Makineni, S.K. and Gault, B. and Chattopadhyay, K. (2019) On the origin of a remarkable increase in the strength and stability of an Al rich Al-Ni eutectic alloy by Zr addition. In: Acta Materialia, 170 . pp. 205-217.

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Official URL: https://dx.doi.org/10.1016/j.actamat.2019.03.025

Abstract

The effect of Zr addition to Al rich binary α-Al - Al 3 Ni eutectic cast alloy (Al-3.1 at. Ni) in enhancing the microstructural stability and strength at high temperature is demonstrated. On subsequent heat treatment after casting, nanometric coherent L1 2 ordered Al 3 Zr precipitates form inside the α-Al that strengthen the alloy. Additionally, remarkable stability of eutectic microstructure was observed even after 100 h of annealing at 400 °C. The synergetic effect of the strengthening of the α-Al matrix by coherent Al 3 Zr precipitates and the low coarsening rate of the Al 3 Ni rods results in a significant increase in high temperature hardness and yield strength of the alloy. The tensile yield strength of the annealed Al-3.1Ni-0.15Zr alloy (400 °C, 10 h) tested at 250 °C is found to be 185 ± 10 MPa, which is 1.5 times higher than the corresponding binary Al-3.1Ni alloy. The experimentally determined average rod size (radius) during annealing at 400 °C follows the classical matrix diffusion controlled LSW-based coarsening model for both binary Al-3.1Ni and ternary Al-3.1Ni-0.15Zr alloys. The calculated coarsening rate constant values based on modified LSW coarsening model are 10.3 and 4.1 nm 3 /s for Al-3.1Ni and Al-3.1Ni-0.15Zr alloys, respectively. Atom probe tomographic (APT) investigations of the heat-treated ternary alloy unambiguously reveal segregation of Zr solute at the αAl/Al 3 Ni interface in addition to the presence of the strengthening Al 3 Zr ordered precipitates in the α-Al matrix. The segregation hinders the interdiffusion of Al and Ni in the eutectic and, thereby, increasing the stability of the eutectic phase at high temperature.

Item Type: Journal Article
Additional Information: The copyright for this article belongs to Acta Materialia Inc
Keywords: Age hardening; Annealing; Binary alloys; Coarsening; Eutectics; Hardness; High resolution transmission electron microscopy; Mechanical properties; Nickel alloys; Ostwald ripening; Precipitation (chemical); Probes; Rate constants; Segregation (metallography); Stability; Ternary alloys; Transmission electron microscopy; Yield stress; Zircaloy, Al-Ni eutectic alloys; Atom probe tomography; Eutectic microstructure; High temperature; High temperature hardness; Microstructural stability; Synergetic effect; Tensile yield strength, Aluminum alloys
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Depositing User: Id for Latest eprints
Date Deposited: 06 May 2019 13:55
Last Modified: 06 May 2019 13:55
URI: http://eprints.iisc.ac.in/id/eprint/62207

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