Spark plasma sintering of ZrB2–ZrC powder mixtures synthesized by MA-SHS in air
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Mechanical activation-assisted self-propagating high-temperature synthesis (MA-SHS) in air was successfully applied to the synthesis of the powder mixtures of ZrB2 and ZrC as a precursor of the ZrB2–ZrC composite. When the powder mixtures of Zr/B/C = 4/2/3–6/10/1 in molar ratio were mechanically activated (MA) by ball milling for 45–60 min and then exposed to air, they self-ignited spontaneously and the self-propagating high-temperature synthesis (SHS) was occurred to form ZrB2 and ZrC. The ZrB2–ZrC composites were produced from these MA-SHS powders by spark plasma sintering (SPS) at 1800 °C for 5–10 min and showed the fine and homogeneous microstructure composed of the <5 μm-sized grains. The mechanical properties of the composites evaluated by Vickers indentation method showed the values of Vickers hardness of 13.6–17.8 GPa and fracture toughness of 2.9–5.1 MPa·m1/2, depending on the molar ratio of ZrB2/ZrC. Thus, the better microstructure and mechanical properties of the ZrB2–ZrC composites were obtained from the MA-SHS powder mixtures, compared with those obtained from the MA powder, the mixing powder and the commercial powder mixtures.
KeywordsFracture Toughness Powder Mixture Spark Plasma Sinter Vickers Hardness Homogeneous Microstructure
The authors gratefully acknowledge support for this research by a Grant-in Aid for Scientific Research (C) (KAKENHI 14550797)) and by Nippon Sheet Glass Foundation for Materials and Engineering, and also the help received from Dr. K. Kurokawa with SPS experiments.
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