抽拉速率对定向凝固Ni-45Ti-5Al合金微观组织的影响  

Effect of withdrawal rate on microstructure of directionally solidified Ni-45Ti-5Al alloys

作　　者：杨春雷[1] 郑立静[1] 李岩[1] 周磊[1] 张虎[1] 

机构地区：[1]北京航空航天大学材料科学与工程学院,北京100191

出　　处：《中国有色金属学报》2011年第11期2763-2768,共6页The Chinese Journal of Nonferrous Metals

摘　　要：采用Bridgman型液态金属冷却定向凝固方法,研究Ni-45Ti-5Al(摩尔分数,%)合金在不同抽拉速率(20、100和200μm/s)下定向凝固后的相组成及其形态特征。结果表明:Ni-45Ti-5Al合金定向凝固生长区呈现明显的柱状晶生长形态,定向效果良好,NiTi基体以[100]方向为择优取向,Ti2Ni析出相沿[111]晶向择优生长。随着抽拉速率的提高,Ti2Ni相更加细小、分散,由在胞晶界上几乎连续分布改变为断续分布。在20～200μm/s的宽生长速率范围内,均以胞状晶形态生长,固/液界面形态没有发生显著变化;随着抽拉速率从20μm/s增加到200μm/s,定向胞晶组织明显细化,平均胞晶间距由85μm减小到25μm。The phase compositions and shapes of directionally solidified（DS） Ni-45Ti-5Al（mole fraction,%） alloys were investigated in the Bridgman liquid-metal-cooling directional-solidification process at withdrawal rates of 20,100 and 200 μm/s.The results show that the columnar grain growth is observed in the DS specimens.The preferred crystal orientation of NiTi matrix is direction and that of Ti2Ni phase precipitated on the matrix is direction.With the increase of withdrawal rate,the Ti2Ni phase becomes finer and distributes from continuously to discontinuously in the intercellular region.When the withdrawal rate varies from 20 μm/s to 200 μm/s,all the solid/liquid interface morphologies are cellular,the DS microstructure is refined obviously and the cellular spacing decreases from 85 μm to 25 μm.

关 键 词：Ni-45Ti-5Al合金 定向凝固 微观组织 固/液界面 

分 类 号：TG146.2[一般工业技术—材料科学与工程]