【摘要】 采用分子动力学模拟了不同温度下0.1%He (原子分数)浓度下含与不含位错α-Fe中He原子偏聚行为和拉伸变形行为。结果表明,当温度为300 K时,预置的位错影响较弱,含与不含位错α-Fe模型中He原子均容易发生自吞噬形成He团簇,He团簇分布弥散且尺寸较小,位错环数目较少;当温度为600 K时,He原子热扩散行为加剧,较多的He原子偏聚到位错,He团簇分布离散且尺寸较大,位错环数目增加。在拉伸变形过程中,位错的存在能够加速He团簇演变成He泡,降低了模型的屈服应力和应变。在低温300 K时,弥散分布的小He团簇容易合并,发生脆性断裂,整个变形过程位错密度较低;在高温600 K时,离散分布的大He泡展现出较好的延展性,发生塑性断裂,整个变形过程中位错大量增殖,塑性较好。更多还原

【Abstract】 The requirement of meeting rapidly growing demand for energy while maintaining environmentally friendly has been motivating the hot research on thermonuclear fusion. One of the key issues in future fusion reactors is that structural materials, especially fusion device first wall material, will suffer from He cumulative effects and atomic displacements from radiation cascades. Such harsh service conditions lead to the formation of He bubbles, which are responsible for severe degradation of the structural materials(e.g., swelling, embrittlement, loss of ductility etc.). It is thus essential to further understand the formation of He bubbles and hardening characteristics for the development of future nuclear materials. In this work, the behaviors of He segregation and tensile deformation have been investigated by molecular dynamics(MD) simulations in α-Fe with and without dislocations(dislocation densities are 0 and 3.36×1011 cm-2, respectively) and at the annealing temperatures of 300 and 600 K with 0.1%He(atomic fraction) injection. The results show that during the process of 300 K annealing, the effect of dislocation is rather weak, and He atoms are easier to form small He clusters by self-trapping. The size of He clusters and the number of dislocation loops are lower. Furthermore, higher temperature can notably intensify He diffusion, and the size of He clusters and the number of dislocation loops both increase at 600 K. In the process of tensile deformation, dislocations can notably accelerate small He clusters to develop into larger He bubbles, which leads to lower yield stress and strain. In addition, at 300 K, the model mainly occurs to brittle fracture and the dislocations density is lower. At 600 K, larger He bubble can promote dislocation multiply and enhance the deformability. Therefore, there exhibits a better plasticity in the model.更多还原