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基于密度泛函理论的第一性原理,探讨了稀土金属元素RE(RE=Y,La,Ce,Lu)合金化对TiAl力学性能的影响。通过计算TiAl合金形成能发现:富Al(Ti8Al7Al)晶体结构比富Ti(Ti_7Al_8Ti)晶体结构更稳定,稀土金属元素RE合金化TiAl合金晶体结构的能量比合金化前有所下降,合金化可提高体系的结构稳定性。通过态密度、Bander电荷密度等分析,发现稀土金属元素RE合金化提高TiAl力学性能的根本原因是:合金化元素RE的电子与周围的Ti原子产生了电荷转移,导致Ti原子失电子数增加,使Ti-Al之间离子性相互作用减弱,共价性相互作用增强,增加TiAl的结构稳定性。同时,RE合金化可降低TiAl合金体系的脆性,增加体系的韧性,其中作用效果从大到小依次是:Y>Ce>La>Lu。
Based on the first principle of density functional theory, the effects of RE (RE = Y, La, Ce, Lu) alloying on the mechanical properties of TiAl were discussed. By calculating the formation of TiAl alloy, it is found that the crystal structure of Al-rich (Ti8Al7Al) crystal is more stable than that of Ti-rich alloy (Ti_7Al_8Ti), and the energy of REAlGaN crystal structure is lower than that before alloying The structural stability of the system. Based on the analysis of state density and Bander charge density, it is found that the fundamental reason why the alloying of rare earth metal RE improves the mechanical properties of TiAl is as follows: the electron of the alloying element RE and the surrounding Ti atoms produce charge transfer, The ionic interaction between Ti-Al weakened covalent interaction increased, increasing the structural stability of TiAl. At the same time, RE alloying can reduce the brittleness of the TiAl alloy system and increase the toughness of the system, the effect of which is descending order: Y> Ce> La> Lu.