NiAl金属间化合物力学性质B，P合金化效应的计算研究

发布时间：2018-01-04 11:07

本文关键词：NiAl金属间化合物力学性质B，P合金化效应的计算研究　出处：《湖南大学》2012年硕士论文　论文类型：学位论文

【摘要】：B2结构NiAl具有高熔点、密度小、导热性好、高温抗氧化性能好等优点，被人们视为用来替代现有Ni基合金的一种理想的航空材料，但NiAl的实际应用却受到金属间化合物本身室温塑、韧性较差的限制。为了改善NiAl金属间化合物的室温脆性，国内外科研人员分别在合金化、细化晶粒等方面开展了大量的研究工作，本文根据现有的实验结果，选取B2-NiAl作为研究对象，根据NiAl的微观结构、物理性质与宏观性能等建立了分析B2-NiAl本征力学性质相对应的物理量，采用第一原理基于虚拟晶体势函数（VCA）近似，计算研究了NiAl金属间化合物力学性质的合金化效应，研究结果期望为高温结构材料性能的优化设计提供理论指导。计算了NiAl金属间化合物的平衡晶格常数、结合能、合金形成热、态密度和能带，发现平衡晶格常数、合金形成热、弹性常数的计算值与实验值和他人计算结果基本吻合。计算了B元素在NiAl合金中的占位情况。从晶体结构优化的结果来看，B占据四面体间隙的γ位置，在结构优化后，B原子倾向到八面体间隙的α位置，由此可以确定B原子合金化后占据尺寸较小的八面体间隙；B合金化后三种位置的形成热与结合能非常结近，从电荷集居数、电荷密度、晶格畸变量及晶体结构优化的结果来看，B原子占据八面体间隙的α位置的可能性较大；计算了B元素合金化前后NiAl合金的电子结构与力学性质，发现B元素合金化降低了NiAl的硬度，但提高延性。计算了P元素在NiAl合金中的五种掺杂位置。从合金能量学的角度来看，P原子占据间隙位置的可能性较小，容易以原子置换的形式存在。从晶格畸变量来看，P原子占据三种间隙位置，相对于P置换Ni或Al原子位置，，晶胞体积变动量要大得多，由此可见P置换Ni或Al原子时，合金化体系的能量低，体系趋于稳定。计算分析了P元素合金化浓度（浓度x≤6.25%）的变化对NiAl合金力学性能的影响。发现P合金化浓度在0.125%(均为原子百分比)附近，B2-NiAl晶体的延性最好、硬度最小，在0.188%附近，B2-NiAl晶体产生强烈的固溶强化硬度急剧增大，但延性下降，在1.25%附近及在3.75%-6.25%区间，B2-NiAl晶体的延性有所改善，但在0.5%附近，B2-NiAl晶体的延性最差。
[Abstract]:The structure of B2 NiAl with high melting point, low density, good thermal conductivity, high temperature antioxidant properties, is an ideal material for aviation people used to replace the existing Ni based alloys, but the actual application of NiAl has been the intermetallic compound itself at room temperature plastic, poor toughness limit. In order to improve the brittleness at room temperature NiAl intermetallic compounds, the domestic and foreign researchers in alloying, grain refinement and other aspects to carry out a lot of research work, according to the experimental results, the B2-NiAl is chosen as the research object, according to the micro structure of NiAl, physical properties and macroscopic properties such as the establishment of B2-NiAl analysis of physical quantity corresponding to the mechanical properties of intrinsic first, using the principle of virtual crystal approximation based on potential function (VCA), study the alloying effect of NiAl intermetallic compound mechanical properties calculation results, expectations for the high temperature structure and material properties The chemical design provides theoretical guidance.
The equilibrium lattice constants, binding energies, alloy formation heat, density of States and energy bands of NiAl intermetallic compounds were calculated. The equilibrium lattice constants, alloy formation heat and elastic constants were calculated.
The calculation of B elements in NiAl alloy occupyingsite. From the crystal structure of the optimization results, B occupy the tetrahedral gamma position in the optimized structure, B atoms tend to a position eight face clearance, which can determine the B atoms occupy the smaller size of the alloy after eight face clearance; B after the three position of the alloy formation heat and binding energy is very near, from the charge population, charge density, lattice parameter and crystal structure of the optimization results, the possibility of a position of eight surface B atoms occupy the gap larger; electronic structure and mechanical properties of NiAl alloy B alloy elements before and after the calculation, found that B element alloying reduces the hardness of NiAl, but improve the ductility.
The position of the P five doped elements in NiAl alloy were calculated. From the perspective of energy alloy, P atoms occupy interstitial positions less likely, easily exist in the form of atomic displacement. The lattice parameter, P atoms occupy the three gap position, relative to the P Ni or replacement of Al atoms, the cell volume variation is much greater, thus P replacement Ni or Al atom, alloying system of low energy, the system tends to be stable.
Analysis of the P element alloying concentration calculation (concentration of X less than or equal to 6.25%) the influence of the changes on the mechanical properties of NiAl alloy. It is found that the alloying of P concentration in 0.125% (both atomic percent) near the ductility of B2-NiAl crystal best, minimum hardness in the vicinity of 0.188%, B2-NiAl crystalline solid solution strengthening hardness increases sharply strong, but the ductility decreased, in the vicinity of 1.25% and in the range of 3.75%-6.25%, the ductility of B2-NiAl crystal has improved, but in the vicinity of 0.5%, the ductility of B2-NiAl crystal is the worst.

【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TG146.15

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