Ti-Al系金属间化合物的价电子结构及其合金化行为

VALENCE ELECTRON STRUCTURES AND ALLOYING BEHAVIOUR OF TI-ALUMINIDES

由固体和分子经验电子理论 (EET)分析了Ti-Al系金属间化合物合金化前后的价电子结构 ,再计算了该系合金各相的均匀变形因子α和解理能Gc 值 ,据此分析了合金化对该系金属间化合物脆性的影响。结果表明 ,常量合金化元素Nb使Ti3Al基合金的α2 相无序化 ,增加了韧的第二相 ,减弱了Ti-Ti共价键 ,综合导致α和Gc 值增大 ,使Ti3Al的脆性有本质改善 ;微量合金化元素Mn减弱了TiAl基合金的Al-Al共价键 ,并诱发孪生 ,使α和Gc 有所提高 ,在一定程度上降低了TiAl的脆性 ;TiAl3极低的α和Gc导致恶劣的本征脆性 。

The valence electron structures, “average deforming factor” α and cleavage energy G c of Ti aluminides affected by alloying are calculated by BLD method of the empirical theory of solids and molecules(EET), and the alloying effects on the embrittlement of Ti aluminides are discussed on the basis of the calculated results. It indicates that Ti 3Al based alloys with the addition of macroalloyed Nb causes a partly disordered α 2 phase, incorporate the toughening phase while weakening the Ti Ti covalent bond, which increases α and G c and thus the embrittlement of Ti 3Al based alloys is basically improved. The addition of Mn in TiAl based alloys weakens the Al Al covalent bond and initiates the twinning, which makes α and G c somewhat enhanced and the embrittlement of TiAl based alloys is improved to some extent. Addition of Mn has no effect on the improvement of embrittlement of low TiAl 3 based alloys because of its very low α and G c values.