Abstract
High temperature tensile tests have been conducted on samples of a Fe-Ni based superalloy, Incoloy A-286, and significant ductility loss has been observed at 1220 °C. Titanium-rich, thin-film-like phase has been found on the inter-granular facets of fracture surfaces. It appears that sulfur content of Ti-rich phase was higher than that of the matrix. At 1220 °C, liquation of Ti-rich phases has resulted in thin-film-like morphology along the grain boundary and caused the ductility loss during tensile deformation.
Highlights
Incoloy A-286 (A-286) is an iron-nickel base, austenitic superalloy containing 25 wt. % of Ni, 15 wt. % of Cr and other minor elements like Ti, Al and Mo
Diffraction patterns and compositional analysis were conducted by transmission electron microscope (TEM, Philips Tecnai F30 FEG-TEM, Amsterdam, The Netherlands) and its EDAX spectrometer
An increase in temperature can soften the material as indicated by the decrease in tensile strength; the ductility of A-286 has been decreased dramatically
Summary
Incoloy A-286 (A-286) is an iron-nickel base, austenitic superalloy containing 25 wt. % of Ni, 15 wt. % of Cr and other minor elements like Ti, Al and Mo. The issue of hot ductility loss has attracted much attention in the superalloy industry, and numerous studies have been reported [6,7,8,9,10,11]. Most of these studies have suggested impurities segregations and formation of precipitates along grain boundaries to be Metals 2015, 5 responsible for loss of ductility. The present article aims to elucidate the underlying mechanisms of high temperature ductility loss for A-286 by examining the fracture surfaces after high temperature tensile tests with scanning electron microscope and transmission electron microscope analysis
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