抽拉速度对Ti-48Al-6Nb-1Cr合金定向凝固组织的影响  

Effect of Drawing Velocity on Structure of Directionally Solidified Ti-48Al-8Nb Alloy

作　　者：刘振伟[1] 沈军[1] 杜玉俊[1] 熊义龙[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《铸造技术》2013年第5期519-522,共4页Foundry Technology

基　　金：国家自然科学基金51174167;凝固技术国家重点实验室自主研究课题项目(63-TP-2011)

摘　　要：采用定向凝固真空电阻炉装置,成功制备了Ti-48Al-6Nb-1Cr合金定向凝固试样,观察了不同抽拉速率下的过渡区、稳态区组织,以及固-液界面形貌。结果表明,当抽拉速率为5μm/s时,合金界面以胞状树枝晶生长,全片层组织(γ+α2)与生长方向几乎全部成45°夹角,合金凝固时的析出相为β相;当抽拉速率增加到25μm/s时,合金界面为明显的树枝晶生长,在初始生长区全片层组织方向与生长方向成0°和45°夹角,随着凝固的进行,组织中与生长方向垂直的片层组织所占比例增加,达到稳定区时,其夹角几乎全变为90°,说明析出相在25μm/s时开始由β相向α相发生转化;当抽拉速率达到50μm/s时,析出相几乎全部以α相生长;而且随着抽拉速率的增加,二次枝晶间距与片层间距减小,组织得到细化。The directionally solidified samples of Ti-48A1-6Nb-1Cr alloys were successfully prepared by a resistance furnace directionally solidified apparatus. The effects of different drawing velocities on the structure of liquid-solid interface and the structures of the transition zone and steady state zone were observed. The interface morphologies were observed as cellular dendrites at 5 μm/s drawing rate and fully-developed dendritic interface at 25 μm/s. The results show that the angle between lamellar （γ＋ α2） orientation and growth direction lay exhibited almost 45° at 5 μm/s, which shows the leading phase growth in microstruetures is β phase. However when the drawing rate is 25 μm/s, the propotion of α2/γ lamellar perpendicular to the growth direction increases ,the lamellar orientation is 0° and 45° on the transition zone and the angle reaches 90° on the steady state zone, the leading phase changes into α phase. When the drawing rate is 50 μm/s, the leading phase is almost α phase. The secondary dendrite arm spacing and the interlamellar spacing decreases with the increase of drawing velocity.

关 键 词：高Nb钛铝合金 定向凝固 全片层组织 

分 类 号：TG244.3[金属学及工艺—铸造]