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Enhancement of High Temperature Strength of 2219 Alloys Through Small Additions of Nb and Zr and a Novel Heat Treatment

Mondol, S and Makineni, S K and Kumar, S and Chattopadhyay, K (2018) Enhancement of High Temperature Strength of 2219 Alloys Through Small Additions of Nb and Zr and a Novel Heat Treatment. In: METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, 49A (7). pp. 3047-3057.

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Official URL: https://dx.doi.org/10.1007/s11661-018-4614-3

Abstract

This paper presents a detailed investigation on the effect of small amount of Nb and Zr additions to 2219 Al alloy coupled with a novel three-stage heat treatment process. The main aim of the work is to increase the high temperature strength of 2219 alloy by introducing thermally stable L1(2) type ordered precipitates in the matrix as well as by reducing the coarsening of metastable strengthening theta aEuro(3) and theta' precipitates. To achieve this, small amounts of Nb and Zr are added to 2219 alloy melt and retained in solid solution by suction casting in a water-cooled copper mould having a cooling rate of 10(2) to 10(3) K/s. The suction cast alloy is directly aged at 673 K (400 A degrees C) to form L1(2) type ordered coherent Al3Zr precipitates. Subsequently, the alloy is solution treated at 808 K (535 A degrees C) for 30 minutes to get supersaturation of Cu in the matrix without significantly affecting the Al3Zr precipitates. Finally, the alloy is aged at 473 K (200 A degrees C), which results in the precipitation of theta aEuro(3) and theta'. Microstructural characterization reveals that theta aEuro(3) and theta' are heterogeneously precipitated on pre-existing uniformly distributed Al3Zr precipitates, which leads to a higher number density of these precipitates. This results in a significant increase in strength at room temperature as well as at 473 K (200 A degrees C) as compared to the 2219 alloy. Furthermore, the alloy remains thermally stable after prolonged exposure at 473 K (200 A degrees C), which is attributed to the elastic strain energy minimization by the conjoint Al3Zr/theta' or Al3Zr/theta aEuro(3) precipitates, and the high Zr and Nb solute-vacancy binding energy, retarding the growth and coarsening of theta aEuro(3) and theta' precipitates.

Item Type: Journal Article
Additional Information: Copy right of this article belong to SPRINGER, 233 SPRING ST, NEW YORK, NY 10013 USA
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Depositing User: Id for Latest eprints
Date Deposited: 25 Jun 2018 15:53
Last Modified: 25 Jun 2018 15:53
URI: http://eprints.iisc.ac.in/id/eprint/60077

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