Effect of Drawing Velocity on the Structure of Directionally Solidified Ti-48Al-8Nb Alloy
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摘要: 采用Bridgeman定向凝固设备成功制备了Ti-48Al-8Nb(原子分数,%)合金定向凝固试样,分析了不同抽拉速度对柱状晶形貌及过渡区、稳态区和淬火区凝固组织的影响。实验结果表明:在不同抽拉速度下,柱晶沿抽拉方向生长良好,柱状晶内部片层取向一致,与生长方向呈45°、90°夹角;当抽拉速度为8μm/s时,固液界面以胞状形貌向前推进,抽拉速度增大到15μm/s时固液界面开始向树枝状生长转化,随着抽拉速度进一步增大,二次枝晶间距逐渐变小,组织明显细化,片层间距显著减小;组织中与生长方向垂直的片层组织所占比例随抽拉速度增大而增加。
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关键词:
- 高Nb-TiAl合金 /
- 定向凝固 /
- 全片层组织
Abstract: Directionally solidified samples of arc-melting Ti-48Al-8Nb(at%) alloy were prepeared through Bridgeman unidirectional solidification technique equipment.The effects of different drawing velocities on the structure of liquid-solid interface and the structures of the transition zone and steady state were observed.The columnar grains grow well along the drawing direction at different drawing velocities.The solid-liquid interface transformed from celluar form to dendritic form when drawing velocity increased from 8μm/s to 50μm/s.The secondary dendrite arm spacing and the interlamellar spacing decreased with the increasing of drawing velocity.In the same time,the propotion of α2/γ lamellar perpendicular to the growth direction increased observably with the increasing of drawing velocity. -
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