Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 717, Issue -, Pages 48-59Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2018.01.057
Keywords
Nickel aluminide, spherical powder; High-resolution electron microscopy; Guinier-Preston zones; Creep
Categories
Funding
- Ministry of Education and Science of the Russian Federation [14.578.21.0260, RFMEFI5817X0260]
- Federal Target Program Research and Development in the Priority Development Areas of the Russian Science and Technology Sector
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The microstructure of Ni alloy produced by hot isostatic pressing (HIP) and selective laser melting (SLM) using pre-alloyed Ni41Al41Cr12Co6 spherical powders was studied by scanning electron microscopy (SEM) and high resolution electron microscopy (HRTEM). In-situ studies of the evolution of the fine structure of Ni41Al41Cr12Co6 alloy during the heating at 20,350... 850 degrees C has been performed. Homogeneous precipitation and growth of the spherical Guinier-Preston zones rich in Cr (size < 5 nm) on concentration fluctuations of dopants in the beta-NiAl matrix by spinodal decomposition was detected in the range of 20-450 degrees C. In addition, the precipitation of the Guinier-Preston zones by heterogeneous nucleation on the crystalline defects of beta-NiAl matrix has been revealed. Prismatic dislocation loops 10-25 nm in size with a stacking fault are formed from a vacancy cluster in the beta-NiAl grain at 750 degrees C. In the 750-850 degrees C interval, heterogeneous nucleation and growth of alpha-Cr nanocrystallites having a prismatic shape and longitudinal size of 20-50 nm was observed on the prismatic dislocation loops. Also, high-temperature strength characteristics of the alloy produced by HIP in the temperature range of 600-1100 degrees C on a Gleeble System 3800 testing system was studied. The high-temperature strength of the HIP samples produced using pre-alloyed spherical powders is higher by 80-100 MPa compared to that of the as-cast alloy.
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