應變場下鎢抗輻照性能的計算機模擬
發(fā)布時間：2018-07-25 18:20
【摘要】：鎢及其合金在未來先進核能系統(tǒng)中具有重要應用前景。其在高能粒子轟擊以及高溫、應力等惡劣環(huán)境條件下發(fā)生的微觀結構和性能變化,將嚴重影響核能系統(tǒng)的長期安全運行。因此,深入開展應力/應變場下鎢中缺陷演化機理和鎢的抗輻照性能評價研究具有重要意義。本論文采用分子動力學模擬方法,較為系統(tǒng)地研究了不同應變狀態(tài)下鎢的抗輻照性能及位錯環(huán)和空洞對其力學性能的影響。主要研究內容和結果如下:1、計算了等靜壓應變下鎢中點缺陷(自間隙子、He間隙子和空位)的形成能和雙空位的結合能以及離位閾能。結果表明:隨著應變由-2%(壓縮)增加到2%(拉伸),自間隙子和He間隙子的形成能逐漸降低,空位形成能逐漸增加。雙空位在拉應變下傾向于以第一近鄰的形式結合,而在壓應變下傾向于以第二近鄰的形式結合。鎢的離位閾能在100或111方向最小,且隨著應變由-2%增加到2%逐漸降低。2、在100、300、500和1000 K下,對比研究了等靜壓應變和平行/垂直于PKA方向單軸應變下鎢中級聯(lián)碰撞行為。結果表明:等靜壓應變對級聯(lián)碰撞的影響大于兩種單軸應變,當單軸應變垂直于PKA方向時,級聯(lián)碰撞隨應變大小變化較小。隨著等靜壓應變或平行于PKA方向單軸應變由-2%增加到2%,Frenkel缺陷對數量、自間隙子團簇比例和缺陷團簇尺寸均逐漸增加,空位團簇比例變化較小。單軸應變會導致自間隙子及其團簇的偏向形成:拉應變越大,沿應變方向的自間隙子及其團簇的比例越大,而壓應變越大,其比例越小。應變對級聯(lián)碰撞的影響隨著溫度的升高而降低。3、研究了300 K下單晶鎢沿100、110和111方向的應力應變關系及位錯環(huán)和空洞的影響。結果表明:單晶鎢沿111方向強度最高,而100方向強度最低。位錯環(huán)和空洞的存在會降低鎢的強度。隨著間隙型位錯環(huán)尺寸增大,抗拉強度逐漸降低。隨著空洞尺寸增大,抗拉強度和彈性模量均逐漸降低。
[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.
【學位授予單位】：中國科學院大學(中國科學院近代物理研究所)
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O469
本文編號：2144645
[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.
【學位授予單位】：中國科學院大學(中國科學院近代物理研究所)
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O469
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