Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification
High Nb-containing TiAl alloys have good oxidation resistance and mechanical properties, but the microstructure and the properties are substantially affected by the segregation. To quantitatively investigate the segregation behavior of Al during solidification, microstructures of directionally solid...
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Wiley
2018-01-01
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| Series: | Advances in Materials Science and Engineering |
| Online Access: | http://dx.doi.org/10.1155/2018/1713835 |
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| author | Xiangjun Xu Rui Hu Junpin Lin Jian Guo |
| author_facet | Xiangjun Xu Rui Hu Junpin Lin Jian Guo |
| author_sort | Xiangjun Xu |
| collection | DOAJ |
| description | High Nb-containing TiAl alloys have good oxidation resistance and mechanical properties, but the microstructure and the properties are substantially affected by the segregation. To quantitatively investigate the segregation behavior of Al during solidification, microstructures of directionally solidified (DS) Ti-45Al-8Nb (in atomic percent) alloy prepared at withdrawing rates of 30 μm/s and 200 μm/s and a temperature gradient of 4200 K/m were observed by optical microscope and electronic probe microanalyzer. The microsegregations were characterized by wave dispersive spectroscopy. The results show that the DS ingots include the no melting zone, directionally solidified zone with columnar grains, mushy zone, and quenched liquid zone. The primary dendritic arm spacings are 353 μm and 144 μm, respectively, for the two ingots. But the solidified microstructures of the ingots are large lamellar colonies, which contain a few B2 patches and γ bands induced by microsegregation. From dendritic zone to columnar zone, the volume fractions of B2 patches and γ bands decrease. The segregation extents of Al and Nb decrease with the increase of solidification rate. There exists an obvious back diffusion process of Al during solidification and cooling after solidification. According to evolution of Al concentration profiles from mushy zone to columnar grain zone, interdiffusion coefficient for Al in β-Ti at near solidus temperature is semiquantitatively calculated, and the value is (6 – 11) × 10−11 m2/s. |
| format | Article |
| id | doaj-art-4ee651a3ac564b7aa87c7bafa6374214 |
| institution | Kabale University |
| issn | 1687-8434 1687-8442 |
| language | English |
| publishDate | 2018-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Advances in Materials Science and Engineering |
| spelling | doaj-art-4ee651a3ac564b7aa87c7bafa63742142025-02-03T01:30:47ZengWileyAdvances in Materials Science and Engineering1687-84341687-84422018-01-01201810.1155/2018/17138351713835Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional SolidificationXiangjun Xu0Rui Hu1Junpin Lin2Jian Guo3School of Materials Science and Engineering, Yangtze Normal University, Chongqing 408100, ChinaState Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, ChinaState Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, ChinaMaterials and Chemistry School, Zhongyuan University of Technology, Zhengzhou 450007, ChinaHigh Nb-containing TiAl alloys have good oxidation resistance and mechanical properties, but the microstructure and the properties are substantially affected by the segregation. To quantitatively investigate the segregation behavior of Al during solidification, microstructures of directionally solidified (DS) Ti-45Al-8Nb (in atomic percent) alloy prepared at withdrawing rates of 30 μm/s and 200 μm/s and a temperature gradient of 4200 K/m were observed by optical microscope and electronic probe microanalyzer. The microsegregations were characterized by wave dispersive spectroscopy. The results show that the DS ingots include the no melting zone, directionally solidified zone with columnar grains, mushy zone, and quenched liquid zone. The primary dendritic arm spacings are 353 μm and 144 μm, respectively, for the two ingots. But the solidified microstructures of the ingots are large lamellar colonies, which contain a few B2 patches and γ bands induced by microsegregation. From dendritic zone to columnar zone, the volume fractions of B2 patches and γ bands decrease. The segregation extents of Al and Nb decrease with the increase of solidification rate. There exists an obvious back diffusion process of Al during solidification and cooling after solidification. According to evolution of Al concentration profiles from mushy zone to columnar grain zone, interdiffusion coefficient for Al in β-Ti at near solidus temperature is semiquantitatively calculated, and the value is (6 – 11) × 10−11 m2/s.http://dx.doi.org/10.1155/2018/1713835 |
| spellingShingle | Xiangjun Xu Rui Hu Junpin Lin Jian Guo Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification Advances in Materials Science and Engineering |
| title | Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification |
| title_full | Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification |
| title_fullStr | Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification |
| title_full_unstemmed | Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification |
| title_short | Evolution of Microstructure and Microsegregation of Ti-45Al-8Nb Alloy during Directional Solidification |
| title_sort | evolution of microstructure and microsegregation of ti 45al 8nb alloy during directional solidification |
| url | http://dx.doi.org/10.1155/2018/1713835 |
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