{"title":"Undercooled liquid state properties and intermetallic compounds growth of ternary Fe-Tb-B alloy","authors":"Y. Ma , Y.P. Zheng , L. Hu , S.H. Liu , W. Zhai","doi":"10.1016/j.intermet.2025.108986","DOIUrl":null,"url":null,"abstract":"<div><div>The substantial undercooling up to 217 K (0.15 times of the alloy liquidus temperature <em>T</em><sub>L</sub>) and rapid solidification of ternary Fe<sub>70</sub>Tb<sub>18</sub>B<sub>12</sub> alloy were achieved through electromagnetic levitation technique. The undercooled liquid surface tension, viscosity and diffusivity were measured versus temperature, from which the activation energies for viscous flow and atomic diffusion were deduced. As undercooling rose, the primary τ<sub>1</sub> (Tb<sub>2</sub>Fe<sub>14</sub>B) intermetallic compound transformed from faceted coarse dendrites to nonfaceted equiaxed grains, attributed to the reduced anisotropic growth velocity between low-index (004) and high-index (214) crystal planes. The dendrite growth velocity of primary τ<sub>1</sub> phase increased as a double-exponential function with its volume fraction up to 47 %. The peri-eutectic structures at small undercoolings showed a regular morphology featured by τ<sub>2</sub> (TbFe<sub>4</sub>B<sub>4</sub>) phase distributing in the interdendritic region of TbFe<sub>2</sub> phase, and their semi-coherent interface following orientation relationship of τ<sub>2</sub>[101]//TbFe<sub>2</sub>[011] and τ<sub>2</sub> <span><math><mrow><mo>(</mo><mrow><mn>11</mn><mover><mn>1</mn><mo>‾</mo></mover></mrow><mo>)</mo></mrow></math></span>//TbFe<sub>2</sub>(100). If undercooling increased, the peri-eutectic τ<sub>2</sub> phase grew as small granules uniformly dispersing on TbFe<sub>2</sub> phase matrix while the interface relationship converted to τ<sub>2</sub>[111]//TbFe<sub>2</sub>[012] and τ<sub>2</sub> <span><math><mrow><mo>(</mo><mrow><mn>1</mn><mover><mn>1</mn><mo>‾</mo></mover><mover><mn>2</mn><mo>‾</mo></mover></mrow><mo>)</mo></mrow></math></span>//TbFe<sub>2</sub> <span><math><mrow><mo>(</mo><mrow><mn>12</mn><mover><mn>1</mn><mo>‾</mo></mover></mrow><mo>)</mo></mrow></math></span>. The corrosion current density of rapid solidification microstructures decreased by two orders of magnitude at the maximum undercooling, which was ascribed to the combination of increased volume fraction, the refinement effect of primary τ<sub>1</sub> intermetallic compound and the formation of irregular peri-eutectic (τ<sub>2</sub>+TbFe<sub>2</sub>) structures.</div></div>","PeriodicalId":331,"journal":{"name":"Intermetallics","volume":"187 ","pages":"Article 108986"},"PeriodicalIF":4.8000,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Intermetallics","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0966979525003516","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
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Abstract
The substantial undercooling up to 217 K (0.15 times of the alloy liquidus temperature TL) and rapid solidification of ternary Fe70Tb18B12 alloy were achieved through electromagnetic levitation technique. The undercooled liquid surface tension, viscosity and diffusivity were measured versus temperature, from which the activation energies for viscous flow and atomic diffusion were deduced. As undercooling rose, the primary τ1 (Tb2Fe14B) intermetallic compound transformed from faceted coarse dendrites to nonfaceted equiaxed grains, attributed to the reduced anisotropic growth velocity between low-index (004) and high-index (214) crystal planes. The dendrite growth velocity of primary τ1 phase increased as a double-exponential function with its volume fraction up to 47 %. The peri-eutectic structures at small undercoolings showed a regular morphology featured by τ2 (TbFe4B4) phase distributing in the interdendritic region of TbFe2 phase, and their semi-coherent interface following orientation relationship of τ2[101]//TbFe2[011] and τ2 //TbFe2(100). If undercooling increased, the peri-eutectic τ2 phase grew as small granules uniformly dispersing on TbFe2 phase matrix while the interface relationship converted to τ2[111]//TbFe2[012] and τ2 //TbFe2 . The corrosion current density of rapid solidification microstructures decreased by two orders of magnitude at the maximum undercooling, which was ascribed to the combination of increased volume fraction, the refinement effect of primary τ1 intermetallic compound and the formation of irregular peri-eutectic (τ2+TbFe2) structures.
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