摘要
采用亚快速定向凝固装置成功地制备了Ti-47.5Al-2Cr-2Nb-0.2B合金定向凝固试样,观察了不同凝固速率下的固液界面形貌、过渡区和稳态区凝固组织。实验结果表明,在2μm/s抽拉速率下,合金界面以胞状界面形态生长,全片层组织(γ+α2)取向与生长方向成0°和45°的夹角,合金凝固时的领先相为β相。在100μm/s凝固速率下,合金界面以枝状形态生长,全片层组织方向与生长方向的夹角为90°,领先相从β相转化为α相。通过将合金中Cr和Nb元素的含量折算成Al的含量,计算Ti-48.3Al合金中α和β相界面生长温度,发现凝固速率达到180μm/s时,领先相可由β相转变为α相,理论计算结果支持实验中的相选择转变过程。
The directionally solidified samples of Ti-47.5Al-2Cr-2Nb-0.2B alloys were successfully prepared by a near-rapid directional solidification apparatus. The interface morphologies were observed as cellular interface at 2μm/s drawing rate and fully-developed dendritic interface at 100μm/s. The angle between lamellar （γ＋ α2 ） orientation and the growth direction lay exhibited 0° or 45° at 2μm/s which showed the leading phase growth in microstructures was β phase. However, at 100μm/s, the lamellar orientation was perpendicular to the growth direction and the angle reached 90° , the leading phase changed to α phase. This phase selection process occurred at 100μm/s matched with the prediction of the theoretical calculation result of 180μm/s, based on the comparison of interface growth temperatures of α and β phase at different drawing rates in TiAl-based alloys under directional solidification.
出处
《航空材料学报》
EI
CAS
CSCD
北大核心
2009年第4期12-16,共5页
Journal of Aeronautical Materials
基金
教育部新世纪优秀人才资助项目(NCET-07-0692)
关键词
TIAL基合金
定向凝固
抽拉速率
全片层组织
TiAl-base alloys, directional solidification, drawing rate, fully lamellar microstructure
