RE(RE=Y,La,Ce,Lu)对TiAl性能影响的计算研究
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摘要
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 first-principles of density functional theory, the effects of rare earth elements RE(RE=Y,La,Ce,Lu)alloying on the mechanical properties of TiAl alloys were discussed. By calculating the formation energy of TiAl alloys, it can be found that: rich Al(Ti8Al7Al) crystal structure is stabler than rich Ti(Ti_7Al_8Ti) crystal structure. The energy of rare earth element RE alloying TiAl alloy crystal structure decreases,compared with the previous alloying, alloying can improve the structural stability of the system. By the density of states and bander charge density analysis, it is found that the underlying reasons for rare earth elements RE alloying TiAl improving the mechanical properties are that electronics and Ti atoms surrounding the alloying elements RE produce a charge transfer, resulting in the increase of Ti atoms lose electrons, so that the ionic interaction between Ti-Al weakens, and the covalent interactions increase,which can enhance the structural stability of TiAl. Meanwhile, RE-alloyed TiAl alloy system can reduce the brittleness and increase the toughness of the system, in which the effect of descending order is:Y>Ce>La>Lu.
Based on first-principles of density functional theory, the effects of rare earth elements RE(RE=Y,La,Ce,Lu)alloying on the mechanical properties of TiAl alloys were discussed. By calculating the formation energy of TiAl alloys, it can be found that: rich Al(Ti8Al7Al) crystal structure is stabler than rich Ti(Ti_7Al_8Ti) crystal structure. The energy of rare earth element RE alloying TiAl alloy crystal structure decreases,compared with the previous alloying, alloying can improve the structural stability of the system. By the density of states and bander charge density analysis, it is found that the underlying reasons for rare earth elements RE alloying TiAl improving the mechanical properties are that electronics and Ti atoms surrounding the alloying elements RE produce a charge transfer, resulting in the increase of Ti atoms lose electrons, so that the ionic interaction between Ti-Al weakens, and the covalent interactions increase,which can enhance the structural stability of TiAl. Meanwhile, RE-alloyed TiAl alloy system can reduce the brittleness and increase the toughness of the system, in which the effect of descending order is:Y>Ce>La>Lu.
引文
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[3]洪雨,吴玉程,李云等.稀土元素La,Ce对机械合金化Ti Al合金显微组织和性能的影响[J].航空材料学报,2009,29(4):17-20.
[4]Li Yongquan,Xie Faqin,Wu Xiangqing.Microstructure and high temperature oxidation resistance of Si-Y codeposition coatings prepared on Ti Al alloy by pack cementation process[J].Transactions of Nonferrous Metals Society of China,2015,25(3):803-810.
[5]宫子琪,陈子勇,柴丽华,等.含Er高Nb-Ti Al基合金的热力学性能[J].材料热处理学报,2014,35(2):205-208.
[6]周鹏,张平则,魏东博,等.Ti Al合金表面Ni Cr Al Y涂层的抗高温氧化性能[J].机械工程材料,2014,35(2):63-67.
[7]Wu Y H,Wang S K,Nam S W,Kim N J.The effect of yttrium addition on the oxidation resistance of EPM Ti Al-based intermctallices[J].Scripta Materialia,2013,48(12):1655-1660.
[8]Lapin J,Gabal Cova Z,Pelachova T.Effect of Y2O3crucible on contamination of directionally solidified intermetallic Ti-46Al-8Nb alloy[J].Intermetallics,2011,19(3):396-403.
[9]Fei Y,Zhu Z S,Wang X N,Li J,et al.Influence of forging process on microstructure and mechanical properties of a new low-cost titanium alloy[J].Chinese Journal of Rare Metals,2013,37(2):186-190.
[10]刘艳梅,武高辉,修子扬,等.Ti和Al反应的动力学分析[J].稀有金属材料与工程,2015,44(3):599-602.
[11]Dong Honggang,Yang Zhonglin,Wang Zengrui,et al.Cu Ti Ni Zr V amorphous alloy foils for vacuum brazing of Ti Al alloy to 40Cr steel[J].Journal of Materials Science&Technology,2015,31(2):217-222.
[12]Qiao H C,Zhao Jibin,Gao Yu.Experimental investigation of laser peening on Ti Al alloy microstructure and properties[J].Chinese Journal of Aeronautics,2015,15(2):609-616.
[13]陶辉锦,孙顺平,张铖铖,等.金属间化合物L10-Ti Al点缺陷浓度的第一原理[J].中国有色金属学报,2014,24(11):2789-2797.
[14]刘友成,周惦武,高丽洁,等.P合金化浓度对Ni Al力学性能影响的第一原理计算[J].稀有金属材料与工程,2013,42(S2):578-581.
[15]Wang H,Xu D S,Rodney D,et al.Atomistic investigation of the annihilation of non-screw dislocation dipoles in Al,Cu,Ni and gamma-Ti Al[J].Modelling&Simulation in Materials Science&Engineering,2013,21(1):25002-25017.
[16]Ren N F,Yang H M,Yuan S Q,et al.Hight emperature mechanical properties and surface fatigue behavior improving of steel alloy vialaser shock peening[J].International Journal of Mechanics and Materials in Design,2014,53(3):452-456.