Micromechanism of High-Temperature Tensile Deformation Behavior of a Directionally Solidified Nickel Base Superalloy

Rai, R K and Sahu, J K and Jena, P S M and Das, S K and Paulose, N and Fernando, D.C (2018) Micromechanism of High-Temperature Tensile Deformation Behavior of a Directionally Solidified Nickel Base Superalloy. Journal of Materials Engineering and Performance, 27(2) (IF-1.331). pp. 659-665.

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High-temperature tensile deformation behavior of directionally solidified nickel base superalloy CM 247 DS is studied by conducting tensile tests in temperature range RT-955 °C employing a constant strain rate of 10−3 s−1 and carrying out extensive electron microscopic examinations to understand the concomitant substructural evolution. The alloy exhibits yield strength anomaly (YSA) behavior like many other superalloys, and the yield strength maxima occur at 750 °C. However, unlike in most of the superalloys, ductility continuously increases with temperature. The deformation behavior of the alloy changes significantly with temperature. Transmission electron microscopic examination confirmed that at lower temperature (≤ 750 °C), γ′ shearing is the dominant deformation mechanism; whereas at temperatures above 750 °C, thermally activated dislocation looping around γ′ precipitate is dominant. Substructures evolved during deformation at 750 °C consists mainly of superlattice stacking faults (SSFs) inside γ′ precipitates, whereas at 850 °C uniform dislocation tangles are observed in γ matrix. Superlattice stacking faults result from shearing of γ′ precipitate by a/3〈112〉 dislocations, which arise from the decomposition of a/2〈110〉 matrix dislocations. YSA in this alloy is attributed to dislocation interactions inside γ′; however, the enhanced ductility even at 750 °C is due to formation of SSFs.

Item Type:Article
Official URL/DOI:https://link.springer.com/article/10.1007/s11665-0...
Uncontrolled Keywords:advanced characterization,electron microscopy, superalloys,superlattice,stacking faults,tensile test
Divisions:Material Science and Technology
ID Code:7788
Deposited By:Sahu A K
Deposited On:06 Apr 2018 12:26
Last Modified:06 Apr 2018 12:26
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