论文部分内容阅读
采用晶体相场模型,分别模拟了小角对称倾侧双晶体系在高温接近熔点温度和达到固-液共存温度时,在外加应变作用下的小角度晶界以及位错的湮没过程.研究表明,没有加外应变时,当体系接近熔点温度情况下,晶界处的晶格位错周围出现预熔化现象,此时预熔化区域内的位错结构并没有发生改变;当温度达到高温固-液共存温度时,预熔化区域明显增大.经高温预熔化后,再施加外应变作用,这时,已存在预熔化的晶界位错发生滑移运动,然后出现位错相遇湮没,晶界消失,同时,伴随的预熔化区域也消失.在预熔化温度情况下的晶界位错的湮没规律基本相同.预熔化温度越接近熔点温度,位错缺陷周围预熔化区域出现晶格原子软化现象越明显,降低了位错周围原子之间的结合强度.这时,在施加外应变作用下,晶格原子对位错滑移运动的阻力降低,位错运动得更快.对于达到高温固-液共存温度情况,此时施加外加应变后,原预熔化区域会出现应变诱发更大面积的预熔化区域.观察到外加应变诱发预熔化区域变化过程中,出现了位错成对地增殖,并发生位错对的旋转和湮没等相互作用;同时,外加应变诱发的预熔化区域的形状随预熔化区内的位错的相互作用而发生变化,出现了预熔化区域相向扩展、连通,然后又分解、分离;尽管这时的预熔化区域形状随外应变作用在不断变化,但此时的预熔化区并不会出现合并消失现象,与较低的预熔化温度的位错运动情况完全不同.
The crystal phase field model was used to simulate the small-angle grain boundaries and dislocation annihilation process under the effect of external strain when the temperature was near the melting temperature and reached the solid-liquid coexistence temperature respectively. In addition, when the system is near the melting point, the pre-melting occurs around the lattice dislocations at the grain boundaries. At this time, the dislocation structure in the pre-melting area does not change. When the temperature reaches high temperature, the solid-liquid coexist At pre-melting temperature, the premelt area increases obviously.After premelting at high temperature and then applying external strain, pre-melted grain boundary dislocation exists in slip movement, and then dislocation encounters annihilation and grain boundary disappears, At the same time, the accompanying pre-melting region also disappears.The rules of annihilation of the grain boundary dislocation at the pre-melting temperature are basically the same.The closer the pre-melting temperature is to the melting temperature, the more obvious the lattice atom softening occurs in the pre-melting region around the dislocation defect , Reducing the bonding strength between the atoms around the dislocations.At this time, under the effect of external strain, the lattice resistance to the dislocation gliding movement of the resistance reduction, dislocation movement faster.For the high temperature When the applied strain is applied, the strain-induced pre-melting region will appear in the pre-melting region.During the pre-melting region induced by the applied strain, the dislocations propagate in pairs And the interaction of dislocation rotation and annihilation occurs. At the same time, the shape of the pre-melting zone induced by the external strain changes with the interaction of dislocations in the pre-melting zone, and the pre-melting zone expands, And then decomposed and separated again. Although the shape of the pre-melted zone changes with the external strain at this time, the pre-melted zone will not disappear at this time, and the dislocation movement with the lower pre-melted temperature will be completely different.