Grain refining mechanism in pure aluminum with nanosized TiN/Ti composite refiner addition

A composite TiN/Ti grain refiner for aluminum and its alloys was prepared through a mixture of micro sized metal powder Ti and nanosized ceramic particles TiN by high energy ball milling. Refinement performance of the TiN/Ti refiner in pure aluminum has been examined in detail by OM, FSEM, EBSD, DSC...

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Veröffentlicht in:Journal of alloys and compounds 2017-03, Vol.699, p.283-290
Hauptverfasser: Li, Xinwei, Cai, Qizhou, Zhao, Bingyi, Li, Bing, Liu, Bo, Ma, Weiliang
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Sprache:eng
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Zusammenfassung:A composite TiN/Ti grain refiner for aluminum and its alloys was prepared through a mixture of micro sized metal powder Ti and nanosized ceramic particles TiN by high energy ball milling. Refinement performance of the TiN/Ti refiner in pure aluminum has been examined in detail by OM, FSEM, EBSD, DSC and TEM methods. Experimental findings indicate that, after adding 0.5 wt% TiN/Ti, the solidification structure of pure aluminum can be refined and the preponderant grain size is reduced to 79.8 μm from more than 1000 μm. TiN/Ti significantly refines the aluminum grain size through not only that it makes undercooling be not measured and increase the nucleation temperature from 671 °C to 681 °C, but also the introduction of potent nuclei. Furthermore, nano TiN particles can act as the nucleus of heterogeneous nucleation of α(Al), the α(Al) grows along the {111} crystal plane from {200} surface of TiN, “Ti-rich transition region” surrounding TiN particles and the heat of reaction between Al and Ti enhances the wettability of TiN in the melt. TiN/Ti refiner significantly refines the aluminum grains. TiN/Ti refiner can provide nano TiN particles to nucleant Al, and Ti to produce “Ti-rich transition region” surrounding TiN particles enhancing the wettability of TiN in the melt. [Display omitted] •TiN/Ti refiner significantly refines the aluminum grains.•TiN/Ti increases the nucleation temperature of aluminum.•Nano TiN particles can act as the nucleus of heterogeneous nucleation of α(Al).•Ti improved the wettability of TiN in the aluminum melt.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2016.12.367