金屬玻璃力學(xué)行為的分子動(dòng)力學(xué)模擬研究
發(fā)布時(shí)間：2018-08-09 20:07
【摘要】：金屬玻璃又稱(chēng)非晶態(tài)合金,是材料家族中的新成員。金屬玻璃由于其特殊的無(wú)序態(tài)金屬鍵結(jié)構(gòu),同時(shí)具有玻璃、金屬、固體和液體特性,表現(xiàn)出非常獨(dú)特的性能。它不僅有望成為一種性能優(yōu)異的新型金屬材料,同時(shí)也是研究材料科學(xué)與凝聚態(tài)物理中一些重要基本問(wèn)題的良好模型體系。金屬玻璃的力學(xué)性能尤其受到了各界人士的關(guān)注,包括超高的強(qiáng)度,超大的彈性和超強(qiáng)的耐磨性等。然而,在金屬玻璃實(shí)現(xiàn)工業(yè)化應(yīng)用過(guò)程中,還有許多困難有待解決,同時(shí),一些基本的科學(xué)問(wèn)題也尚不清晰。如金屬玻璃增韌的方法和有效性,剪切帶的結(jié)構(gòu)特性,金屬玻璃的小尺寸效應(yīng),以及金屬玻璃的微觀變形單元與宏觀變形之間的關(guān)聯(lián)等。本文通過(guò)分子動(dòng)力學(xué)模擬方法,系統(tǒng)研究了在金屬玻璃,主要是CuZr體系中,通過(guò)結(jié)構(gòu)調(diào)控的方法,觀察到不同的力學(xué)變形行為,并解釋各自的變形機(jī)理。得到的主要結(jié)果如下所示：(1)通過(guò)分子動(dòng)力學(xué)方法,系統(tǒng)研究了Cu64Zr36以及Cu40Zr60兩種成分中的拉伸變形行為與微觀STZ的演化之間的關(guān)系。研究發(fā)現(xiàn)在應(yīng)力達(dá)到最大值之后,樣品中開(kāi)始出現(xiàn)一些原子,它們具有較大的局域原子應(yīng)變(或位移),可將其定義為S原子。在最大應(yīng)力之后,S原子率先在“孔隙區(qū)”附近,以及一些類(lèi)液形的Voronoi構(gòu)型中產(chǎn)生。當(dāng)進(jìn)一步的變形時(shí),一些非“孔隙區(qū)”區(qū)域,或構(gòu)型為類(lèi)固形的Voronoi構(gòu)型中,也會(huì)產(chǎn)生S原子。此后,伴隨著剪切帶的開(kāi)始萌生,S原子主要集中在剪切帶上產(chǎn)生�？梢詫TZ的大小定義為S原子以及其周?chē)罱徳拥目倲?shù),相互連接的原子屬于同一個(gè)STZ。計(jì)算發(fā)現(xiàn)平均STZ大小與應(yīng)變的大小密切相關(guān),在7%到12%應(yīng)變范圍內(nèi),該值從17±3變化到106±6。以上結(jié)果部分解釋了為什么不同的實(shí)驗(yàn)測(cè)試方法會(huì)得出不一樣的STZ的大小。接下來(lái),我們進(jìn)一步分析了隨著應(yīng)變的增加,STZ大小的分布的變化情況。研究發(fā)現(xiàn),完整剪切帶的形成與大尺寸STZ的產(chǎn)生密切相關(guān)。我們的研究結(jié)果有助于進(jìn)一步推進(jìn)構(gòu)建宏觀剪切帶與微觀STZ之間關(guān)聯(lián)的研究。(2)通過(guò)分子動(dòng)力學(xué)方法,在Cu64Zr36,Cu36Zr64,以及Ni40Zr60三種體系中研究了單根剪切帶的力學(xué)變形行為,發(fā)現(xiàn)它在拉伸條件下應(yīng)力應(yīng)變曲線中沒(méi)有出現(xiàn)“應(yīng)力過(guò)沖”現(xiàn)象,并且經(jīng)過(guò)20%變形后宏觀樣品形狀未發(fā)生變化,表現(xiàn)出一種標(biāo)準(zhǔn)的均勻變形行為。并且,這種特殊的變形行為不受尺寸因素的制約,在更大尺寸的體系中也觀察到了相同的現(xiàn)象,暗示著這個(gè)現(xiàn)象很可能擴(kuò)展至宏觀尺度上。同時(shí),通過(guò)對(duì)剪切帶在不同溫度下退火,可以實(shí)現(xiàn)變形模式的連續(xù)轉(zhuǎn)變。此外,通過(guò)快速冷卻的方法,同樣可以獲得“類(lèi)剪切帶”的結(jié)構(gòu),實(shí)現(xiàn)均勻變形行為。并且,利用Voronoi多面體以及“孔隙區(qū)”分析方法系統(tǒng)研究了樣品的結(jié)構(gòu)隨著不同退火溫度以及冷卻速率的變化。發(fā)現(xiàn),“類(lèi)剪切帶”結(jié)構(gòu)的樣品中,其“孔隙區(qū)”以及“類(lèi)液區(qū)”具有較大的相對(duì)原子含量,這使其更加傾向于發(fā)生均勻變形。以上結(jié)論在Cu64Zr36,Cu36Zr64,以及Ni40Zr60三種體系中都成立,并得到了實(shí)驗(yàn)上的驗(yàn)證。我們的研究結(jié)果對(duì)于在實(shí)驗(yàn)中大尺寸樣品制備出具有宏觀塑性性能的金屬玻璃材料,提供了一些新的思路。(3)通過(guò)分子動(dòng)力學(xué)方法,系統(tǒng)研究了Cu20Zr80,Cu40Zr60,Cu50Zr50,Cu64Zr36以及Cu80Zr20五個(gè)成分中不同厚度金屬玻璃薄膜樣品的拉伸力學(xué)行為。研究發(fā)現(xiàn)在Cu-Zr體系中的五個(gè)成分中,都發(fā)生了隨著薄膜厚度的減小,其變形模式發(fā)生從局域化變形到非局域化變形的轉(zhuǎn)變。研究證明了這種與尺寸相關(guān)的變形模式的變化,與變形過(guò)程中的應(yīng)變能有關(guān)。當(dāng)累積的應(yīng)變能足夠大,則材料發(fā)生局域化變形,而若累積的能量不足,則發(fā)生非局域化變形。同時(shí),不同成分中,其臨界尺寸會(huì)隨著成分發(fā)生變化,并且被證明與形成單個(gè)S原子(或者說(shuō)STZ)所需要的激活能量有關(guān)。激活能越高,臨界尺寸越小。對(duì)CusoZrso不同厚度金屬玻璃薄膜的研究,還發(fā)現(xiàn),厚度越小,它的彈性模量越低,強(qiáng)度越低,密度越低,泊松比越低。這種性能上的差異,是由于具有低密度的表面層(約0.4納米)的相對(duì)原子含量,在整體樣品中所占據(jù)的比例不同所致。我們的研究結(jié)果有助于推進(jìn)對(duì)尺寸導(dǎo)致的變形模式轉(zhuǎn)變的進(jìn)一步的研究。(4)通過(guò)分子動(dòng)力學(xué)方法,系統(tǒng)研究了以Cu64Zr36(A), CusoZrso(B), Cu4oZr6o(C)三種單相材料為基礎(chǔ),構(gòu)建出不同種類(lèi)多層膜結(jié)構(gòu)復(fù)合材料的拉伸力學(xué)行為。我們通過(guò)不同的組合模式,來(lái)對(duì)材料的強(qiáng)度進(jìn)行調(diào)控,并以此實(shí)現(xiàn)對(duì)材料變形模式的調(diào)控。研究發(fā)現(xiàn)多層膜的層數(shù)是決定變形模式轉(zhuǎn)變的重要因素,當(dāng)層數(shù)超過(guò)或等于七層時(shí),在A相與C相的組合,以及A相與B相的組合中,都能觀察到非局域化變形模式的發(fā)生。進(jìn)一步的分析發(fā)現(xiàn),多層膜的變形模式與構(gòu)成它的單元(即單層膜)的變形模式有所關(guān)聯(lián),但并不能由其決定。此外,多層膜的變形模式可以通過(guò)能量判據(jù)和不均勻程度分析來(lái)定性地解釋。我們的研究結(jié)果有助于推進(jìn)在純非晶態(tài)結(jié)構(gòu)中增強(qiáng)塑性的進(jìn)一步的探索。
[Abstract]:Metallic glass, also known as amorphous alloy, is a new member of the family of materials. Metal glass, due to its special disorder metal bond structure, has the characteristics of glass, metal, solid and liquid, shows very unique properties. It is not only expected to be a new type of metal material with excellent performance, but also the research of material science and coagulation. A good model system for some important basic problems in state physics. The mechanical properties of metal glass are especially concerned by people from all walks of life, including ultra high strength, super elasticity and super strong wear resistance. However, there are still many difficulties to be solved in the process of industrial application of metal glass. At the same time, some basic scientific questions are needed. The method and effectiveness of toughening of metal glass, the structural characteristics of the shear band, the small size effect of the metallic glass, and the correlation between the microscopic deformation unit and the macroscopic deformation of the metal glass are also studied. This paper systematically studies the structure of metal glass, mainly in the CuZr system, through the molecular dynamics simulation method. The main results are as follows: (1) the relationship between the tensile deformation behavior of the Cu64Zr36 and the two components of the Cu40Zr60 and the evolution of the microcosmic STZ is systematically studied by molecular dynamics method. The study finds that the maximum stress is reached. After that, the samples begin to appear some atoms, which have larger local atomic strain (or displacement), which can be defined as S atoms. After the maximum stress, S atoms take the lead in the formation of the "pore zone", and some liquid like Voronoi configurations. When further deformation, some non "pore zone" regions, or the configuration of the type are solid. In the form of the Voronoi configuration, the S atom is also produced. Thereafter, with the beginning of the shear band, the S atom is mainly concentrated on the shear band. The size of the STZ can be defined as the S atom and the total number of adjacent adjacent atoms around it. The interconnected atoms belong to the same STZ. calculation and found that the average STZ size is closely related to the size of the strain. In the 7% to 12% strain range, the value of the value from 17 + 3 to 106 + 6. explains why different experimental methods will produce different sizes of STZ. Next, we further analyze the changes in the distribution of the STZ size as the strain increases. The study shows that the formation of the complete shear band and the large size STZ The results of our study are helpful to further promote the study of the association between macroscopic shear bands and microcosmic STZ. (2) the mechanical deformation of single shear bands in the Cu64Zr36, Cu36Zr64 and Ni40Zr60 systems is studied by molecular dynamics method, and it is found that it is in the stress-strain curve under the tensile condition. There is no "stress overshoot" phenomenon, and the shape of the macro sample has not changed after 20% deformation, showing a standard uniform deformation behavior. Moreover, this special deformation behavior is not restricted by the size factor, and the same phenomenon is observed in the larger size system, suggesting that this phenomenon is likely to expand to the extent. At the same time, the shear band can be transformed continuously by annealing at different temperatures. In addition, the structure of the "shear band" can be obtained by rapid cooling, and the Voronoi polyhedron and the pore zone analysis method are used to study the samples. With the change of the annealing temperature and cooling rate, it is found that in the samples of the "class shear band" structure, the "pore zone" and the "liquid like zone" have larger relative atomic content, which makes it more inclined to have uniform deformation. The above conclusion is established in the three systems of Cu64Zr36, Cu36Zr64, and Ni40Zr60. Experimental verification. Our results provide some new ideas for the preparation of metal glass materials with macro plastic properties in large size samples in the experiment. (3) through molecular dynamics, the metal glass films with different thickness of Cu20Zr80, Cu40Zr60, Cu50Zr50, Cu64Zr36 and Cu80Zr20 are systematically studied. The tensile mechanical behavior of the sample is found. It is found that in the five components of the Cu-Zr system, the deformation modes occur from localized deformation to non localized deformation with the decrease of the thickness of the film. The study shows that the change of the deformation mode related to the size dependent deformation process is related to the strain energy during the deformation process. When the energy is large enough, the material is localized and deformed, and the localized deformation occurs if the accumulated energy is insufficient. At the same time, the critical size varies with the composition in the different components, and is proved to be related to the activation energy required for the formation of a single S atom (or STZ). The higher the activation energy, the smaller the critical size. CusoZrso The study of metal glass films with different thickness also found that the smaller the thickness, the lower the modulus, the lower the strength, the lower the density and the lower the Poisson's ratio. The difference in performance is due to the relative atomic content of the low density surface layer (about 0.4 nanometers) and the different proportion in the whole body. Further research on the transformation of deformation patterns caused by size is further promoted. (4) through molecular dynamics, the tensile mechanical behavior of different kinds of multilayer composite materials is constructed based on Cu64Zr36 (A), CusoZrso (B), Cu4oZr6o (C), and the tensile mechanical behavior of the composite materials of different kinds of multilayer films is constructed. The strength of the material is regulated and adjusted to control the deformation mode of the material. It is found that the number of layers is an important factor determining the transformation of the deformation mode. When the number of layers exceeds or equal to seven layers, the combination of the A phase and the C phase and the combination of the A phase and the B phase can observe the occurrence of the non localized deformation mode. It is found that the deformation mode of the multilayer film is related to the deformation mode of its unit (the monolayer), but it can not be determined by it. In addition, the deformation mode of the multilayer film can be explained qualitatively by the energy criterion and the analysis of the inhomogeneity. Our research results help to promote the enhancement of the plasticity in the pure amorphous structure. A step of exploration.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG139.8
，
本文編號(hào)：2175173
[Abstract]:Metallic glass, also known as amorphous alloy, is a new member of the family of materials. Metal glass, due to its special disorder metal bond structure, has the characteristics of glass, metal, solid and liquid, shows very unique properties. It is not only expected to be a new type of metal material with excellent performance, but also the research of material science and coagulation. A good model system for some important basic problems in state physics. The mechanical properties of metal glass are especially concerned by people from all walks of life, including ultra high strength, super elasticity and super strong wear resistance. However, there are still many difficulties to be solved in the process of industrial application of metal glass. At the same time, some basic scientific questions are needed. The method and effectiveness of toughening of metal glass, the structural characteristics of the shear band, the small size effect of the metallic glass, and the correlation between the microscopic deformation unit and the macroscopic deformation of the metal glass are also studied. This paper systematically studies the structure of metal glass, mainly in the CuZr system, through the molecular dynamics simulation method. The main results are as follows: (1) the relationship between the tensile deformation behavior of the Cu64Zr36 and the two components of the Cu40Zr60 and the evolution of the microcosmic STZ is systematically studied by molecular dynamics method. The study finds that the maximum stress is reached. After that, the samples begin to appear some atoms, which have larger local atomic strain (or displacement), which can be defined as S atoms. After the maximum stress, S atoms take the lead in the formation of the "pore zone", and some liquid like Voronoi configurations. When further deformation, some non "pore zone" regions, or the configuration of the type are solid. In the form of the Voronoi configuration, the S atom is also produced. Thereafter, with the beginning of the shear band, the S atom is mainly concentrated on the shear band. The size of the STZ can be defined as the S atom and the total number of adjacent adjacent atoms around it. The interconnected atoms belong to the same STZ. calculation and found that the average STZ size is closely related to the size of the strain. In the 7% to 12% strain range, the value of the value from 17 + 3 to 106 + 6. explains why different experimental methods will produce different sizes of STZ. Next, we further analyze the changes in the distribution of the STZ size as the strain increases. The study shows that the formation of the complete shear band and the large size STZ The results of our study are helpful to further promote the study of the association between macroscopic shear bands and microcosmic STZ. (2) the mechanical deformation of single shear bands in the Cu64Zr36, Cu36Zr64 and Ni40Zr60 systems is studied by molecular dynamics method, and it is found that it is in the stress-strain curve under the tensile condition. There is no "stress overshoot" phenomenon, and the shape of the macro sample has not changed after 20% deformation, showing a standard uniform deformation behavior. Moreover, this special deformation behavior is not restricted by the size factor, and the same phenomenon is observed in the larger size system, suggesting that this phenomenon is likely to expand to the extent. At the same time, the shear band can be transformed continuously by annealing at different temperatures. In addition, the structure of the "shear band" can be obtained by rapid cooling, and the Voronoi polyhedron and the pore zone analysis method are used to study the samples. With the change of the annealing temperature and cooling rate, it is found that in the samples of the "class shear band" structure, the "pore zone" and the "liquid like zone" have larger relative atomic content, which makes it more inclined to have uniform deformation. The above conclusion is established in the three systems of Cu64Zr36, Cu36Zr64, and Ni40Zr60. Experimental verification. Our results provide some new ideas for the preparation of metal glass materials with macro plastic properties in large size samples in the experiment. (3) through molecular dynamics, the metal glass films with different thickness of Cu20Zr80, Cu40Zr60, Cu50Zr50, Cu64Zr36 and Cu80Zr20 are systematically studied. The tensile mechanical behavior of the sample is found. It is found that in the five components of the Cu-Zr system, the deformation modes occur from localized deformation to non localized deformation with the decrease of the thickness of the film. The study shows that the change of the deformation mode related to the size dependent deformation process is related to the strain energy during the deformation process. When the energy is large enough, the material is localized and deformed, and the localized deformation occurs if the accumulated energy is insufficient. At the same time, the critical size varies with the composition in the different components, and is proved to be related to the activation energy required for the formation of a single S atom (or STZ). The higher the activation energy, the smaller the critical size. CusoZrso The study of metal glass films with different thickness also found that the smaller the thickness, the lower the modulus, the lower the strength, the lower the density and the lower the Poisson's ratio. The difference in performance is due to the relative atomic content of the low density surface layer (about 0.4 nanometers) and the different proportion in the whole body. Further research on the transformation of deformation patterns caused by size is further promoted. (4) through molecular dynamics, the tensile mechanical behavior of different kinds of multilayer composite materials is constructed based on Cu64Zr36 (A), CusoZrso (B), Cu4oZr6o (C), and the tensile mechanical behavior of the composite materials of different kinds of multilayer films is constructed. The strength of the material is regulated and adjusted to control the deformation mode of the material. It is found that the number of layers is an important factor determining the transformation of the deformation mode. When the number of layers exceeds or equal to seven layers, the combination of the A phase and the C phase and the combination of the A phase and the B phase can observe the occurrence of the non localized deformation mode. It is found that the deformation mode of the multilayer film is related to the deformation mode of its unit (the monolayer), but it can not be determined by it. In addition, the deformation mode of the multilayer film can be explained qualitatively by the energy criterion and the analysis of the inhomogeneity. Our research results help to promote the enhancement of the plasticity in the pure amorphous structure. A step of exploration.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG139.8
，
本文編號(hào)：2175173
本文鏈接：http://sikaile.net/kejilunwen/jiagonggongyi/2175173.html
最近更新
教材專(zhuān)著
