Microstructures of Low Angle Boundaries of a Third Generation Single Crystal Superalloy DD9

Abstract:

The microstructures of low angle boundaries (LABs) of a third generation single crystal superalloy DD9 in as-cast state and after different heat treatment processes were studied by optical microscopy (OM) and field emission scanning electron microscopy (FESEM). The results showed that the as-cast LABs of DD9 alloy consisted of rod-like and bulk γ' phases with γ matrix between them, and there were eutectic γ-γ' precipitating at the LABs, as well as small amounts of discrete distribution of carbides. The γ' phase locateed at the grain boundaries was larger than that distributed on both sides of the grain boundaries. After the solution heat treatment, as-cast eutectic γ-γ' at LABs dissolved completely, and rod-like γ' phase was still found at some LABs. Meanwhile, the LABs were inclined to be straight compared to the as-cast state. The primary aging heat treatment made γ' phase at the LABs dissolved completely, and the secondary aging heat treatment resulted little change in the morphology of the LABs. Thus, the effect of the primary aging heat treatment on the microstructures of the LABs was greater than that of the secondary aging heat treatment.

• Periodical: Materials Science Forum (Volume 898)
• Pages: 413-421
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.898.413
• Online since: June 2017
• Authors: Wan Peng Yang*, Jia Rong Li, Shi Zhong Liu, Jin Qian Zhao, Zhen Xue Shi, Xiao Guang Wang
• Keywords: DD9, Low Angle Boundary, Microstructure, Single Crystal Superalloy

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