Abnormal WC crystal growth from liquid Co flux occurs via eta phase decomposition
| Autor: | Finn Giuliani, Maxim Vreeswijk, Alexandre Kot, Samuel A. Humphry-Baker |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
education.field_of_study
Materials science 020502 materials Diffusion Population Analytical chemistry Crystal growth 02 engineering and technology General Medicine Decomposition Carbide 0205 materials engineering Phase (matter) Metallography education 0912 Materials Engineering Materials Eutectic system |
| Popis: | The growth mechanism of large WC crystals from a liquid Co-based flux is identified. This is achieved by systematically varying the growth temperature and Co content from 1200 to 1400 °C and 70–83 at.% respectively. Crystal growth was characterised using metallography and X-ray diffraction. The WC grains were bimodally distributed, consisting of a smaller (10–20 μm) population of grains, which nucleated homogenously from the liquid, and a secondary population of abnormally large grains, several millimetres in size. The abnormal grains nucleated on the (W,Co)6C eta phase, and subsequently consumed it through a carburisation reaction. The size of abnormal grains was enhanced by adopting the eutectic composition, such that the first solid phase to form was the eta phase, whilst at the same time cooling slowly through the eta➔WC transformation temperature, at ~1300 °C. This growth mechanism could be exploited for a variety of metal carbides with similarly sluggish diffusion rates. |
| Databáze: | OpenAIRE |
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