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Tensile Properties of Ni-Based Superalloy 720Li: Temperature and Strain Rate Effects

Gopinath, K and Gogia, AK and Kamat, SV and Balamuralikrishnan, R and Ramamurty, U (2008) Tensile Properties of Ni-Based Superalloy 720Li: Temperature and Strain Rate Effects. In: Metallurgical and Materials Transactions A, 39 (10). pp. 2340-2350.

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Abstract

Tensile properties, deformation, and fracture behavior of a wrought nickel-base superalloy 720Li have been studied in standard solutionized and two-stage-aged condition in the temperature range of $25oC$ to $750^oC$. Effect of strain rate on tensile behavior was assessed at $25^oC$, 44006oC$, and $750^oC$ at five strain rates that range between $10^{-5} s^{-1}$ and $10^{-1} s^{-1}$. The yield strength and ultimate tensile strength of the alloy remained unaffected by temperature until about $600^oC$ and $500^oC$, respectively, typical of superalloys strengthened by fine and coherent intermetallic $Ni_3Al$-based precipitates. The flow stress of the alloy was found to be insensitive to the strain rates studied at $25^oC$ and $400^oC$. However, at $750^oC$, the flow stresses showed strain rate sensitivity at strain rates $<10^{-3} s^{-1}$. The strain hardening behavior at $25^oC$ and $400^oC$ were similar. At $750^oC$, stain hardening was observed only at strain rates $>10^{-3} s^{-1}$, and at lower strain rates, tensile instability was seen to set in immediately after yielding. The alloy exhibited ductile dimple fracture at all the temperatures and strain rates studied. Microstructural investigations indicate that in regimes where flow stresses are insensitive to strain rate, deformation occurs through heterogeneous planar slip, whereas in strain rate sensitive regimes,thermally activated diffusion processes promote homogeneous deformation.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to The Minerals, Metals & Materials Society.
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 15 May 2009 05:50
Last Modified: 19 Sep 2010 04:49
URI: http://eprints.iisc.ernet.in/id/eprint/15726

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