The effect of ball-milling time and annealing temperature on fracture toughness of Ni-3 wt.% SiC using small punch testing

A set of dispersion strengthened Ni-3 wt.% SiC samples have been prepared via a powder metallurgy route for an application in molten salt reactor (MSR) systems. A mixture of 97 wt.% Ni and 3 wt.% SiC powder was prepared by varying the ball-milling time (8, 24, 36 and 48 h). The ball-milling process...

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Bibliographic Details
Published in:Materials characterization 2018-04, Vol.138, p.289-295
Main Authors: Yang, Chao, Wei, Tao, Muránsky, Ondrej, Carr, David, Huang, Hefei, Zhou, Xingtai
Format: Article
Language:English
Subjects:
ANNEALING
BACKSCATTERING
DISTRIBUTION
ELECTRON DIFFRACTION
FRACTURE PROPERTIES
GRAIN BOUNDARIES
MATERIALS SCIENCE
Molten salt reactor
MOLTEN SALT REACTORS
Ni-SiC
NICKEL ADDITIONS
POWDER METALLURGY
SCANNING ELECTRON MICROSCOPY
SEGREGATION
SILICON CARBIDES
Small punch
TRANSMISSION ELECTRON MICROSCOPY
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Summary:A set of dispersion strengthened Ni-3 wt.% SiC samples have been prepared via a powder metallurgy route for an application in molten salt reactor (MSR) systems. A mixture of 97 wt.% Ni and 3 wt.% SiC powder was prepared by varying the ball-milling time (8, 24, 36 and 48 h). The ball-milling process was followed by powder consolidation using spark plasma sintering (SPS) and rapid cooling to room temperature. The samples were then annealed at different temperatures (300 °C, 700 °C and 850 °C). The fracture behaviour of the Ni-3 wt.% SiC samples was investigated using the Small Punch Test (SPT). A scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) and electron back-scatter diffraction (EBSD), as well as transmission electron microscopy (TEM) were employed to examine the microstructure of the tested Ni-3 wt.% SiC samples. The obtained results show that the SPT fracture energy is strongly dependent on the grain size of Ni matrix, which is affected by ball-milling times and annealing temperature. It has been further found that the segregation of large SiC particles at grain boundaries promotes intergranular fracture and thus significantly reduces the fracture energy. The results indicate that the distribution and size of SiC particles at grain boundary is mainly affected by the ball-milling time. Hence, the ball-milling time governs the fracture toughness of Ni-3 wt.% SiC samples. •The fracture energy of Ni-SiC is strongly dependent on the grain size of Ni matrix•The ball-milling time governs the fracture behaviour of Ni-3 wt.% SiC•A higher proportion of big SiC particles at grain boundary is responsible for a lower fracture toughness
ISSN:1044-5803
1873-4189
DOI:10.1016/j.matchar.2018.02.024