铌、碳在TiAl合金扩散的原理研究

采用第一原理赝势平面波方法研究了碳原子在TiAl(010)表面及有Nb的TiAl(010)表面的扩散机理。通过晶胞最终能量和形成能计算得出,Nb—C复合渗虽然使TiAl(010)面晶胞总能量上升,但却使其形成能下降,即Nb—C共渗后的TiAl合金稳定性提高。电子结构分析发现:渗Nb可使Ti (3d)—Al(3p)键合作用减弱;渗Nb后使费米能低能级处电子成键数目多,稳定性增强,因此从电子层面说明了Nb元素对渗碳具有促进作用。

First-principles Study on Diffusion Mechanisms of Nb and C Atoms on TiAl(010)Surface

This paper investigates diffusion of C atoms on TiAl (010) surface with and without Nb which is transition metal ele- ment by using first-principles pseudopotential plane-wave meth- od.By analyzing final energy and forming enthalpy,it is found that the duplex treatment of niobizing and carburization makes the final energy of the surface cell of TiAl (010) enhanced,but it makes forming enthalpy descended,so it makes the stability of cell impioved.By analyzing electron structure shows that niobiz- ing can weaken the effects of bond of Ti (3d)-Al (3p),this can improve the brittleness.Niobizing also can make the number of electron bonding which locates at thereinafter Fermi level in- creased,improve the stability,and so this can explain the action of Nb promote carburization on the standpoint of electron aspect.