Effect of grain size on the hardness and reactivity of plasma-sintered beryllium
Introduction
Fusion reactors require functional materials, such as those used for generating tritium and as a neutron multiplier, to be loaded as in the form of pebbles in the planned water-cooled solid breeder concept. Beryllium (Be) and its intermetallic compounds have been extensively investigated as materials for neutron multipliers, and a variety aspects, such as mechanical properties [1], [2], reactivity [3], irradiation properties [4], and synthesis methods [5], [6] have been studied. However, the high brittleness of intermetallic beryllium compounds (i.e., beryllides) precludes their fabrication as pebbles and blocks. Nevertheless, researchers have fabricated beryllide pebbles (1 mm diameter) by a novel method that combines plasma sintering [7], [8] and rotating electrode methods [9]. Another drawback associated with beryllides is that Be in beryllides [10] is easily oxidized. Beryllium oxidation occurs predominantly at the grain boundaries; however, the presence of impurities can lead to the formation of porous and non-protective oxide layers. In case of pure metals, such as Ni [11] or Cu [12], diffusion across the grain boundary of the metal surface with smaller grain sizes results in a decrease of activation energy for oxidation of the metals. However, the influence of the grain boundary on the oxidation behavior of the beryllium is still unsatisfactory despite the reactivity of multipliers has increasingly become important in fields of not only the fusion reactor but a boron neutron capture therapy machine [13].
In this study, the effect of grain size on mechanical and chemical properties of plasma-sintered Be (PS-Be)at 1073 and 1273 K in dry air and in the presence of Ar gas/1% H2O, respectively, has been investigated.
Section snippets
Experimental
Beryllium powders of various sizes were used to fabricate four PS-Be samples. First, Be powders (>99.5% pure) with four different particle sizes, <20 (Be20), <45 (Be45), <75 (Be75), and <150 (Be150) μm (Materion, USA), were prepared. The distribution in size was measured by a laser diffraction particle size analyzer (SALD-3100, Shimadzu, Japan). These powders were independently sintered in their plasma state under identical conditions to give the samples PS-Be20, PS-Be45, PS-Be75, and PS-Be150 (
Powder characterization and sinterability
To investigate the effect of grain-size on the properties of PS-Be, we first prepared Be powders with four different sizes. These powders are categorized on the basis of their size: <20 μm (Be20), <45 μm (Be45), <75 μm (Be75), and <150 μm (Be150). Size distribution profile and SEM images of Be20, Be45, Be75, and Be150 (Fig. 1) reveal that the particle size distribution, while being broad, are a clear distinguishing feature of the powders, while particle shape across different powders are similar.
Conclusions
The effect of grain size on the mechanical and chemical properties of plasma-sintered beryllium (PS-Be). Beryllium powders of different particle sizes, i.e., <20 μm (Be20), <45 μm (Be45), <75 μm (Be75), and <150 μm (Be150) are sintered under identical conditions to fabricate PS-Be20, PS-Be45, PS-Be75, and PS-Be150. Analysis of sinterability, hardness, and reactivity of Be lead to the following conclusions:
- (1)
Synthesized PS-Be samples possess significantly high density. Samples with smaller grain size,
References (21)
- et al.
J. Alloys Compd.
(2013) - et al.
J. Nucl. Mater.
(2007) - et al.
Fus. Eng. Des.
(2012) - et al.
J. Alloys Compd.
(2013) - et al.
J. Nucl. Mater.
(2013) - et al.
J. Alloys Compd.
(2013) - et al.
J. Alloys Compd.
(2014) - et al.
J. Nucl. Mater.
(2013) - et al.
Metallography
(1980) - et al.
Fus. Eng. Des.
(2013)
Cited by (24)
Reactivity of beryllium in aqueous solution from acidic to basic pH
2023, Journal of Electroanalytical ChemistryA microcompression study on the mechanical properties and fracture behavior of Be–Al and Be–AlSi10Mg alloys fabricated by laser solid forming
2022, Materials Science and Engineering: ACitation Excerpt :Their strengths are mainly influenced by the strengths of the Al matrix and the interaction between the Al matrix and the Be reinforcements. The Al matrix is usually strengthened through dislocation-related micromechanics, including grain boundary strengthening (Hall-Petch strengthening), precipitation strengthening (Orowan strengthening), and dislocation strengthening induced by the relaxation of thermal expansion mismatch [29,30]. Meanwhile, the interaction between Al matrices and Be particles is commonly described as the modified shear lag model.
Evaluation of several conditioning matrices for the management of radioactive metal beryllium wastes
2022, Journal of Nuclear MaterialsCitation Excerpt :It is also under study as interesting material for the future fusion power reactors. In the International Thermonuclear Experimental Reactor, Be constitutes the main plasma facing for the first wall of the tokamak and the neutron multiplier in the breeding blanket [6–10]. The use of beryllium in fission and fusion reactors will make it radioactive by neutron irradiation.
Microstructural evolution and hardness of as-cast Be-Al-Sc-Zr alloy processed by laser surface remelting
2021, Chinese Journal of Aeronautics