马氏体钢中铬原子对空位-氦团簇作用的第一性原理研究

First⁃principles study on the effect of Cr atoms on vacancy⁃helium clusters in RAFM alloy

利用第一性原理计算方法研究了Cr原子对纯Fe和Fe9Cr合金中空位-氦(VacHe_(n))团簇类型缺陷的影响.研究发现小的He_(n)团簇也会引起强烈的晶格畸变,尤其是He_(n)团簇周围的自间隙Fe原子倾向于产生自发射现象,即:Fe原子仍然倾向于从He_(n)团簇附近转移到无穷远,但当n>2时Fe9Cr的空位形成能低于纯Fe,这表明Cr原子可以在一定程度上提高Fe原子在He_(n)团簇周围的稳定性.另外,VacHe_(n)在纯Fe中比在Fe9Cr合金中更稳定,并且Fe9Cr合金中的空位团簇对He原子的俘获能的明显小于纯Fe中的俘获能,这表明溶解Cr原子的斥力会削弱He原子的聚集.研究结果有助于阐释He泡马氏体钢的生长机理及其对其稳定性和机械性能的影响.

First⁃principles calculations were used to investigate the effect of Cr atoms on He⁃induced vacancy⁃like defects in pure Fe and Fe9Cr alloys.It was observed that the small He_(n)clusters were able to induce strong lattice distortions,and the emis⁃sion of a self⁃interstitial Fe atom located at the adjacent He_(n) cluster was energetically favorable.For n>2,vacancy formation energies of Fe9Cr were lower than those of pure Fe,which suggested that Cr atoms could effectively enhance the stability of Fe atoms around He_(n) clusters.The trapping energy of He atom by the vacancy clusters in Fe9Cr alloy was significantly lower than that in pure Fe.It was shown that the repulsive force of dissolved Cr atoms would weaken the aggregation of He atoms.VacHe_(n) was more stable in pure Fe than in Fe9Cr alloy.These results help to provide additional insights into the behavior of He in irra⁃diated Fe and Fe9Cr surfaces,and are necessary for the interpretation of the growth of the He bubble.