کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5436393 | 1509550 | 2017 | 11 صفحه PDF | دانلود رایگان |
The loss of ductility in the high strength polycrystalline superalloy 720Li is studied in air between room temperature and 1000 °C. Tensile ductility is influenced profoundly by the environment, leading to a pronounced minimum at 750 °C. A relationship between tensile ductility and oxidation kinetics is identified. The physical factors responsible for the ductility dip are established using energy-dispersive X-ray spectroscopy, nanoscale secondary ion mass spectrometry and the analysis of electron backscatter diffraction patterns. Embrittlement results from internal intergranular oxidation along the γ-grain boundaries, and in particular, at incoherent interfaces of the primary γⲠprecipitates with the matrix phase. These fail under local microstresses arising from the accumulation of dislocations during slip-assisted grain boundary sliding. Above 850 °C, ductility is restored because the accumulation of dislocations at grain boundaries is no longer prevalent.
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Journal: Acta Materialia - Volume 126, March 2017, Pages 361-371