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钛铝金属间化合物具有优异的高温性能,但室温脆性限制了其广泛应用.为探寻脆性的解决办法,需在原子尺度上理解其变形机理.作为位错与孪晶机制系统研究的一部分,本文采用分子动力学及静力学方法模拟了钛铝011]超位错的形核与运动.研究发现,与普通无序合金不同,有序的钛铝金属间化合物中沿正反[011]方向剪切时,超位错表现出非对称行为.分析表明,这种差异源自与面心立方结构相比钛铝的L10有序化使晶格对称性降低,导致沿相反方向剪切时呈现不同的屈服应力、应变、位错芯的分解及位错运动规律.沿[011]剪切变形时,晶体中4根偏位错在同一滑移面上相继形核,构成同心椭圆形超位错环.超位错芯由4根肖克莱偏位错及将其隔开的3种广义层错组成.超位错环扩张过程中其分解方式依赖于其在环上的部位(位错取向)及剪切方向.刃取向及附近的超位错呈4重分解,60°附近逐渐转变为3重分解,最后在30°附近变成2重分解.超位错开动可具有不同的临界剪切应力,与启动时的分解方式及剪切方向有关,当SISF领先时其临界应力较低.
Titanium-aluminum intermetallic compounds have excellent high-temperature properties, but brittleness at room temperature limits its wide application.In order to explore the solution of brittleness, it is necessary to understand the deformation mechanism at the atomic scale.As part of the systematic study of dislocation and twinning mechanism, Molecular dynamics and static methods were used to simulate the nucleation and movement of super-dislocations of titanium-aluminum (011) .It was found that, unlike the normal disordered alloys, ordered titanium-aluminum intermetallics The super-dislocations exhibit asymmetric behavior when sliced, and the analysis shows that this difference results from the L10 ordering of titanium-aluminum in the face-centered cubic structure that results in a decrease in lattice symmetry leading to differences in shear in the opposite direction , Yield stress, strain, decomposition of dislocation core and dislocation motion.When the shear deformation along [011], four displacement dislocations in the crystal nucleate successively on the same slip plane, forming concentric elliptical super-dislocations Ring.The super-dislocation core consists of four Shockley deviators and three generalized layer faults that separate them.The disintegration of the super-dislocation ring depends on its position on the ring (dislocation orientation ) And shear direction. The blade orientation and nearby super-dislocations were quadrupled , Gradually changing to 3-fold decomposition near 60 ° and finally becoming 2-fold decomposition near 30 ° .Step dislocation can have different critical shear stress, which is related to the decomposition mode and shear direction at startup. When SISF leads The critical stress is lower.