TC4合金渗硼层TiB和TiB2价电子结构与渗层硬化

Valence Electron Structures of TiB and TiB2 and Hardening on Boronizing Layer of TC4 Alloy

摘要:

计算了TiB与TiB2的价电子结构，研究了TiB、TiB2的价电子结构与TC4合金渗硼层硬化的关系。研究发现：TC4合金渗硼层的TiB2和TiB相中B-B原子键合力最强，且远大于合金基体组成原子的键合力；TiB2相最强共价键的共价电子对数为0.5554，TiB相最强共价键的共价电子对数为0.4042，因此TiB2相对基体的硬化作用更强；TiB2相的原子状态组数σN为123，而TiB相的原子状态组数σN为19，所以TiB2相的稳定性更高；由相成键能力F的计算可知，从热力学角度看，渗层中TiB应比TiB2多；共价键空间分布决定了TiB晶体易沿[010]晶向生长成短纤维状，而TiB2相易于生成高对称性的粒状或球状，故TiB2比TiB更有利于硬化基体。

Abstract:

Based on the empirical electron theory of solids and molecules(EET), the valence electron structures(VESs) of TiB and TiB2 were calculated, and then the relationship between their VESs and boronizing layer hardening of TC4 alloy was analyzed. The B-B bonds of TiB and TiB2 on boronizing layer are the strongest, and they are far bigger than that of the strongest bond of the substrate. The strongest bond of TiB2 (=0.555 4) is stronger than that of TiB (=0.404 2), so the strengthening effect of TiB2 on substrate is stronger. From the number of atom state group of phases σN, we can know that the stability of TiB2 is far bigger than that of TiB. The space distribution of the covalence bonds decides that it is easy for TiB to grow along the [010] direction and form short threadiness, while for TiB2 it is easy to form high symmetry granulous or globular shape, therefore TiB2 is better than TiB at substrate hardening and the improvement of wear-resisting. From the forming-bond ability of phases F, we can know that the amount of TiB is more than that of TiB2 on the boronizing layer.