Evolution of new topologically close-packed phases P and R upon long-term isothermal aging of laser powder bed fusion processed Hastelloy X

Agrawal, S and Avadhani, GS and Suwas, S (2024) Evolution of new topologically close-packed phases P and R upon long-term isothermal aging of laser powder bed fusion processed Hastelloy X. In: Journal of Alloys and Compounds, 1010 .

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Abstract

The evolution of secondary phases and the microstructure-property relationship of laser powder bed fusion processed Hastelloy X during long-term isothermal aging have been studied. Hastelloy X was subjected to prolonged thermal exposure at two different temperatures, 800 °C and 950 °C, for 500 h in each case to explore the distribution and evolution of secondary phases. A thorough microstructural investigation employing transmission electron microscopy exhibited the evolution of M23C6 carbides along with the topologically close-packed (TCP) phases such as µ, R and P. At 800 °C, the intergranular formation of M23C6 was characterized by a perfect cube-on-cube orientation relationship with the matrix phase. Moreover, at the same temperature, the µ phase is uniformly distributed in the matrix as well as in the intergranular regime. The main finding includes the evolution of P and R phases at 950 °C. At this temperature, the presence of new TCP phases, i.e., R and P (which had not been previously observed in Hastelloy X), evolved at the intergranular regime, whereas no carbides or the µ phase were evident. Also, at this temperature, the matrix region was found to be devoid of any kind of precipitation. All the TCP phases were characterized by planar defects attributed to accommodate the lattice misfit strain. The room temperature and elevated temperature (800 °C) tensile tests demonstrated higher yield strength and lower elongation of the 800 °C specimen compared to the 950 °C specimen, which was attributed to the excessive matrix and intergranular precipitation. © 2024 Elsevier B.V.

Item Type:	Journal Article
Publication:	Journal of Alloys and Compounds
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Elsevier Ltd.
Keywords:	High resolution transmission electron microscopy; Laser materials processing; Lattice mismatch, 950° C; Hastelloy X; Intergranular; Isothermal ageing; Laser powder bed fusion; Laser powders; Orientation relationship; Powder bed; Topologically close packed phase; Transmission electron, Tensile testing
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	12 Dec 2024 17:48
Last Modified:	12 Dec 2024 17:48
URI:	http://eprints.iisc.ac.in/id/eprint/87010

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