应变场下钨抗辐照性能的计算机模拟

发布时间：2018-07-25 18:20

【摘要】：钨及其合金在未来先进核能系统中具有重要应用前景。其在高能粒子轰击以及高温、应力等恶劣环境条件下发生的微观结构和性能变化,将严重影响核能系统的长期安全运行。因此,深入开展应力/应变场下钨中缺陷演化机理和钨的抗辐照性能评价研究具有重要意义。本论文采用分子动力学模拟方法,较为系统地研究了不同应变状态下钨的抗辐照性能及位错环和空洞对其力学性能的影响。主要研究内容和结果如下:1、计算了等静压应变下钨中点缺陷(自间隙子、He间隙子和空位)的形成能和双空位的结合能以及离位阈能。结果表明:随着应变由-2%(压缩)增加到2%(拉伸),自间隙子和He间隙子的形成能逐渐降低,空位形成能逐渐增加。双空位在拉应变下倾向于以第一近邻的形式结合,而在压应变下倾向于以第二近邻的形式结合。钨的离位阈能在100或111方向最小,且随着应变由-2%增加到2%逐渐降低。2、在100、300、500和1000 K下,对比研究了等静压应变和平行/垂直于PKA方向单轴应变下钨中级联碰撞行为。结果表明:等静压应变对级联碰撞的影响大于两种单轴应变,当单轴应变垂直于PKA方向时,级联碰撞随应变大小变化较小。随着等静压应变或平行于PKA方向单轴应变由-2%增加到2%,Frenkel缺陷对数量、自间隙子团簇比例和缺陷团簇尺寸均逐渐增加,空位团簇比例变化较小。单轴应变会导致自间隙子及其团簇的偏向形成:拉应变越大,沿应变方向的自间隙子及其团簇的比例越大,而压应变越大,其比例越小。应变对级联碰撞的影响随着温度的升高而降低。3、研究了300 K下单晶钨沿100、110和111方向的应力应变关系及位错环和空洞的影响。结果表明:单晶钨沿111方向强度最高,而100方向强度最低。位错环和空洞的存在会降低钨的强度。随着间隙型位错环尺寸增大,抗拉强度逐渐降低。随着空洞尺寸增大,抗拉强度和弹性模量均逐渐降低。
[Abstract]:Tungsten and its alloys have important application prospects in the future advanced nuclear power system. The microstructure and performance changes of nuclear energy system under the condition of high energy particle bombardment, high temperature, stress and so on will seriously affect the long-term safe operation of nuclear energy system. Therefore, it is of great significance to study the evolution mechanism of tungsten defects and the radiation resistance of tungsten under stress / strain field. In this paper, the radiation resistance of tungsten under different strain conditions and the effects of dislocation rings and voids on the mechanical properties of tungsten were systematically studied by molecular dynamics simulation. The main contents and results are as follows: 1. The formation energy, binding energy and departure threshold energy of the middle point defects (self-gap he gap and vacancy) of tungsten under isostatic strain are calculated. The results show that with the increase of strain from -2% (compression) to 2% (tensile), the formation energy of self-gap and he gap decreases gradually, and the vacancy formation energy increases gradually. The double vacancies tend to combine in the form of first nearest neighbor under tensile strain and in the form of second nearest neighbor under compressive strain. The departure threshold energy of tungsten is the smallest in the direction of 100 or 111, and decreases gradually with the increase of strain from -2% to 2%. At 100300500 and 1000 K, the intermediate collision behavior of tungsten at isostatic strain and parallel / vertical uniaxial strain in PKA direction is studied. The results show that the influence of isostatic strain on cascade collision is greater than that of two kinds of uniaxial strain. When uniaxial strain is perpendicular to the direction of PKA, the effect of cascade strain on cascade collision is small. With the increase of isostatic strain or uniaxial strain parallel to the PKA direction from -2% to 2% Frenkel defect pairs, the self-clearance cluster ratio and defect cluster size increase gradually, while the vacancy cluster ratio changes slightly. Uniaxial strain will lead to the formation of self-gap and its cluster bias: the larger the tensile strain, the larger the ratio of self-gap and its clusters along the direction of strain, and the smaller the ratio of compressive strain is. The effect of strain on cascade collision decreases with the increase of temperature. The stress-strain relationship of single crystal tungsten along 100110 and 111 directions and the effects of dislocation rings and voids at 300K are studied. The results show that the strength of single crystal tungsten is the highest in the direction of 111 and the lowest in the direction of 100. The existence of dislocation rings and voids will reduce the strength of tungsten. With the increase of the size of the gap dislocation ring, the tensile strength decreases gradually. The tensile strength and elastic modulus decrease gradually with the increase of cavity size.
【学位授予单位】：中国科学院大学(中国科学院近代物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O469

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