本文選題：鈦鋁層合復(fù)合材料 + 分子模擬　； 參考：《哈爾濱工業(yè)大學(xué)》2015年碩士論文

【摘要】：本文主要研究了鈦鋁層合復(fù)合材料的單軸拉伸力學(xué)性能。通過(guò)采用分子動(dòng)力學(xué)模擬的方法分析了鈦鋁各單獨(dú)材料及其層合材料在單軸拉伸過(guò)程中內(nèi)部位錯(cuò)的演化情況。分析了由于兩邊添加保護(hù)相鋁后,鈦內(nèi)部位錯(cuò)演化的改變;以及當(dāng)保護(hù)相鋁晶粒尺寸減小時(shí),對(duì)鈦內(nèi)部位錯(cuò)演化所造成的影響。為此,本文首先建立了9晶粒的多晶鈦模型,以及4晶粒和9晶粒的多晶鋁模型。借助Voronoi原理,使模擬盒子被劃分為幾個(gè)不同的晶粒部分,然后再將初始建立好的足夠大單晶模板按照一定旋轉(zhuǎn)角投影到各晶粒部分中,逐一完成各晶粒的建模過(guò)程。所完成多晶模型形狀均為密排方向平行于軋制面的柱狀晶,且滿足各晶粒在平面方向不聯(lián)通的條件。對(duì)多晶模型進(jìn)行單軸拉伸模擬,發(fā)現(xiàn)拉伸曲線可以很好的表現(xiàn)出材料的塑性階段,且4晶粒的多晶鋁與9晶粒的多晶鋁拉伸曲線形狀大致相似,表示本文所建立的多晶模型合理。為能夠合理分析鈦鋁單獨(dú)材料及其層合材料在拉伸過(guò)程中位錯(cuò)的演化情況,本文采用了一種參數(shù)化方法,先根據(jù)模型在拉伸過(guò)程每一步中各個(gè)晶粒內(nèi)所有原子所處位置偏離完整晶體時(shí)對(duì)應(yīng)原子所應(yīng)處在位置的距離,得出一個(gè)g參數(shù),再通過(guò)分析g參數(shù)的變化曲線得出總的結(jié)構(gòu)位錯(cuò)在每一步的演化程度。其中對(duì)單晶而言,只需對(duì)整個(gè)模型計(jì)算一個(gè)g參數(shù);而對(duì)多晶而言,需要對(duì)每個(gè)晶粒分別計(jì)算一個(gè)g參數(shù)。利用g參數(shù)分析兩種邊界條件下單晶鋁單軸拉伸的模擬情況,可以發(fā)現(xiàn)g參數(shù)在結(jié)構(gòu)處于彈性段時(shí)基本保持接近零的直線,而當(dāng)拉伸曲線達(dá)到最高點(diǎn)結(jié)構(gòu)失效時(shí)則突然發(fā)生階躍,表示此時(shí)結(jié)構(gòu)內(nèi)部有大量位錯(cuò)萌生運(yùn)動(dòng)并直接導(dǎo)致結(jié)構(gòu)塑性失穩(wěn)。利用g參數(shù)分析單獨(dú)4晶粒和9晶粒鋁的拉伸破壞情況。發(fā)現(xiàn)應(yīng)變直到15%時(shí),g曲線都基本成平緩上升趨勢(shì),沒(méi)有較大階躍,這表示鋁結(jié)構(gòu)雖然發(fā)生塑性變形,但位錯(cuò)并未大量演化,結(jié)構(gòu)仍能繼續(xù)承載。利用g參數(shù)分析單獨(dú)9晶粒鈦的拉伸破壞情況,發(fā)現(xiàn)g曲線上升陡峭,且基本在應(yīng)變達(dá)到7%時(shí)所有晶粒全部失效,表明鈦的塑性性能遠(yuǎn)差于鋁。利用g參數(shù)分析當(dāng)兩邊層合4晶粒鋁后9晶粒鈦的拉伸破壞情況,相比鈦單獨(dú)拉伸而言,g曲線有明顯變平緩趨勢(shì),整體結(jié)構(gòu)的破壞應(yīng)變推遲到11.3%,表明與保護(hù)相鋁的層合作用可以顯著提升鈦的拉伸塑形性能。利用g參數(shù)分析當(dāng)兩邊層合9晶粒鋁后9晶粒鈦的拉伸破壞情況,相比之前兩邊4晶粒鋁層合時(shí),鈦的拉伸塑形又有一定提高,破壞應(yīng)變達(dá)到13.4%,表明層合結(jié)構(gòu)中保護(hù)相為細(xì)晶鋁時(shí)更能提高承載相鈦的拉伸塑形性能。
[Abstract]:The uniaxial tensile mechanical properties of Ti-Al laminated composites were studied in this paper. The evolution of internal dislocations in the uniaxial tensile process of individual titanium and aluminum materials and their laminated materials was analyzed by molecular dynamics simulation. The changes of dislocation evolution in titanium due to the addition of aluminum on both sides of the protective phase and the effect on the evolution of dislocation in titanium are analyzed when the grain size of aluminum in the protective phase is reduced. For this reason, the polycrystalline titanium model of 9 grain and the polycrystalline aluminum model of 4 grain and 9 grain are established in this paper. With the help of Voronoi principle, the simulation box is divided into several different grain parts, and then the initial large enough single crystal template is projected to each grain part according to a certain rotation angle, and the modeling process of each grain is completed one by one. The completed polycrystalline models are all columnar crystals with dense rows parallel to the rolling surface and satisfy the condition that the grains are not connected in the plane direction. The uniaxial tensile simulation of the polycrystalline model shows that the tensile curve can well show the plastic stage of the material, and the shape of the tensile curve of the 4 grain polycrystalline aluminum is similar to that of the 9 grain polycrystalline aluminum. It is shown that the polycrystalline model established in this paper is reasonable. In order to reasonably analyze the evolution of dislocations in the tensile process of titanium-aluminum single material and its laminates, a parameterized method is used in this paper. Firstly, a g parameter is obtained according to the distance of the position of all atoms in each grain deviating from the complete crystal when the model is located in each step of the tensile process. The evolution degree of the total structural dislocation in each step is obtained by analyzing the variation curve of the g parameter. For single crystals, only one g parameter is needed for the whole model, while for polycrystals, one g parameter is needed for each grain. By using g parameter to analyze the simulation of uniaxial tension of single crystal aluminum under two boundary conditions, it can be found that g parameter basically keeps a straight line close to zero when the structure is in the elastic region. When the tensile curve reaches the highest point, the structural failure occurs step by step, indicating that there is a large number of dislocation initiation motion in the structure, which directly leads to the plastic instability of the structure. The tensile failure of single 4 grain and 9 grain aluminum was analyzed by g parameter. It is found that the strain and g curves have a gentle upward trend until 15, which indicates that although plastic deformation occurs in the aluminum structure, the dislocation does not evolve in large quantities and the structure can continue to carry the load. By using g parameter to analyze the tensile failure of single 9 grain titanium, it is found that the g curve rises steeply and almost all the grains fail when the strain reaches 7, which indicates that the plastic property of titanium is much worse than that of aluminum. By using g parameter to analyze the tensile failure of titanium with 9 grain after laminated with 4 grain aluminum on both sides, the g curve has an obvious tendency of flattening compared with that of titanium alone. The failure strain of the whole structure was delayed to 11. 3, which indicates that the tensile plastic properties of titanium can be significantly improved by the cooperation of the protective aluminum layer. The tensile failure of titanium was analyzed by using g parameter when both sides were laminated with 9 grain aluminum. Compared with the former four grain aluminum layers, the tensile shape of titanium was improved to a certain extent. The failure strain reached 13.4, which indicates that the tensile molding properties of titanium bearing phase can be improved more when the protective phase in the laminated structure is fine crystalline aluminum.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TB331

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本文編號(hào)：2030608