【摘要】：鎢及其合金在未來(lái)先進(jìn)核能系統(tǒng)中具有重要應(yīng)用前景。其在高能粒子轟擊以及高溫、應(yīng)力等惡劣環(huán)境條件下發(fā)生的微觀結(jié)構(gòu)和性能變化,將嚴(yán)重影響核能系統(tǒng)的長(zhǎng)期安全運(yùn)行。因此,深入開(kāi)展應(yīng)力/應(yīng)變場(chǎng)下鎢中缺陷演化機(jī)理和鎢的抗輻照性能評(píng)價(jià)研究具有重要意義。本論文采用分子動(dòng)力學(xué)模擬方法,較為系統(tǒng)地研究了不同應(yīng)變狀態(tài)下鎢的抗輻照性能及位錯(cuò)環(huán)和空洞對(duì)其力學(xué)性能的影響。主要研究?jī)?nèi)容和結(jié)果如下:1、計(jì)算了等靜壓應(yīng)變下鎢中點(diǎn)缺陷(自間隙子、He間隙子和空位)的形成能和雙空位的結(jié)合能以及離位閾能。結(jié)果表明:隨著應(yīng)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(yīng)變下傾向于以第一近鄰的形式結(jié)合,而在壓應(yīng)變下傾向于以第二近鄰的形式結(jié)合。鎢的離位閾能在100或111方向最小,且隨著應(yīng)變由-2%增加到2%逐漸降低。2、在100、300、500和1000 K下,對(duì)比研究了等靜壓應(yīng)變和平行/垂直于PKA方向單軸應(yīng)變下鎢中級(jí)聯(lián)碰撞行為。結(jié)果表明:等靜壓應(yīng)變對(duì)級(jí)聯(lián)碰撞的影響大于兩種單軸應(yīng)變,當(dāng)單軸應(yīng)變垂直于PKA方向時(shí),級(jí)聯(lián)碰撞隨應(yīng)變大小變化較小。隨著等靜壓應(yīng)變或平行于PKA方向單軸應(yīng)變由-2%增加到2%,Frenkel缺陷對(duì)數(shù)量、自間隙子團(tuán)簇比例和缺陷團(tuán)簇尺寸均逐漸增加,空位團(tuán)簇比例變化較小。單軸應(yīng)變會(huì)導(dǎo)致自間隙子及其團(tuán)簇的偏向形成:拉應(yīng)變?cè)酱?沿應(yīng)變方向的自間隙子及其團(tuán)簇的比例越大,而壓應(yīng)變?cè)酱?其比例越小。應(yīng)變對(duì)級(jí)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(yīng)力應(yīng)變關(guān)系及位錯(cuò)環(huán)和空洞的影響。結(jié)果表明:單晶鎢沿111方向強(qiáng)度最高,而100方向強(qiáng)度最低。位錯(cuò)環(huán)和空洞的存在會(huì)降低鎢的強(qiáng)度。隨著間隙型位錯(cuò)環(huán)尺寸增大,抗拉強(qiáng)度逐漸降低。隨著空洞尺寸增大,抗拉強(qiáng)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(xué)位授予單位】：中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院近代物理研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：O469

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