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| EFFECTS OF TEMPERATURE GRADIENT ON LAMEL-LAR ORIENTATIONS OF DIRECTIONAL SOLIDIFIED TiAl–BASED ALLOY |
| XIAO Zhixia, ZHENG Lijing, YANG Lili, YAN Jie, ZHANG Hu |
Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and
Engineering, Beihang University, Beijing, 100191 |
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Cite this article:
XIAO Zhixia ZHENG Lijing YANG Lili YAN Jie ZHANG Hu. EFFECTS OF TEMPERATURE GRADIENT ON LAMEL-LAR ORIENTATIONS OF DIRECTIONAL SOLIDIFIED TiAl–BASED ALLOY. Acta Metall Sin, 2010, 46(10): 1223-1229.
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Abstract Directional solidification experiments under heating temperatures of 1580℃ and 1650℃ were performed on Ti–47Al–2Cr–2Nb alloy in order to obtain the evolution of lamellar grains. From microstructural analysis in the mushy zone of directional solidified ingots, β phase was firstly solidified, then α phase was formed through peritectic reaction; α phase depended on the pre–existed β phase on which it nucleated, and only one of the 12 α orientation variants was selected during solid state β→ α transformations. As the average temperature gradient of the mushy zone was increased from 40 K/cm to 160 K/cm, the solidification interface morphologies were changed from columnar dendrite to celluar dendrite. Eliminating the influence of cutting plane to the γ–lamella orientation, it was shown that the columnar lamellar grains with an angle of approximately 74? to growth direction gradually overgrew the ones with the angle of nearly 45? to the growth direction at the withdrawal rate of 1 mm/min and temperature gradient of 40 K/cm. Increasing temperature gradient to 160 K/cm, the grains with the angle of about 74? progressively rejected other with the angle of nearly 90? to the growth direction. Calculation of the β dendrite preferred growth orientation indicated that β dendrites tend to grow along the <110>β orientation at the present solidification experiments. Increasing temperature gradient, the preferred growth tendency of dendrite became more drastically, other orientations, such as the <001>β directional orientation, could rapidly be replaced.
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Received: 28 June 2010
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| About author: 肖志霞, 女, 1984年生, 博士生 |
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