An innovative method for the microstructural modification of TiAl alloy solidified via direct electric current application
An innovative method for the microstructural modification of TiAl alloy solidified via direct electric current application
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一种通过直流电流凝固 TiAl 合金微观结构改性的创新方法
DOI：
10.1016/j.jmst.2018.06.016
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发表时间：
2019-01-01
影响因子：
10.9
通讯作者：
Fu, Hengzhi
中科院分区：
文献类型：
--
作者：
Chen, Zhanxing;Ding, Hongsheng;Fu, Hengzhi
直流电作用下凝固的Ti-48Al-2Cr-2Nb合金组织细小均匀，无偏析。我们观察到，随着电流密度的增加，晶粒度和片层间距开始减小，随后又增大。改变α(2)相(Ti3Al)的含量也可以得到类似的趋势。采用定向凝固工艺，在电流密度为32-mA/mm(2)时，柱状晶组织转变为等轴晶组织。在电流密度为mA/mm(2)时，获得了最小横截面尺寸为460um的高位错密度。电流通过焦耳加热改变了临界晶核的自由能和温度，导致了柱状晶组织向等轴晶组织的转变。电流密度越大，形核率越高，过冷和温度梯度共同作用于初生相的长大，最终在临界电流密度为96 mA/mm(2)时，初生相粗化。位错的攀移和交叉滑移以及晶界的迁移最终导致TiAl合金片层间距的变化。(C)2018年由爱思唯尔有限公司代表《材料科学与技术杂志》编辑部出版。
Ti-48Al-2Cr-2Nb alloy solidified with the application of direct electric current has a refined and homogeneous microstructure without segregation. We observed an initial decrease followed by a subsequent increase in grain size and lamellar spacing, with the increase in current density. Similar trend can also be obtained by varying the amount of alpha(2)-phase (Ti3Al). Using a directional solidification processing method, the columnar crystal microstructure transforms into an equiaxed crystal microstructure at a current density of 32-64 mA/mm(2). High dislocation density is also introduced with a minimum cross-sectional grain size of 460 mu m at a current density of 64 mA/mm(2). The application of electric current alters the free energy of the critical nucleus and temperature via joule heating, causing a transformation from a columnar grain microstructure into an equiaxed grain microstructure. The increase in current density leads to a rise of the nucleation rate, and a resulting undercooling combined with temperature gradient contribute to growth of the primary phase, which finally results in grain coarsening at a critical current density of 96 mA/mm(2). The climb and cross-slip of dislocation and the migration of grain boundary ultimately create variable lamellae spacing of TiAl alloy. (C) 2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.