W-Cu复合材料动力喷涂制备及力学性能研究

发布时间：2018-03-08 10:33

本文选题：W-Cu复合涂层　切入点：动态力学性能　出处：《北京理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：W-Cu复合材料具有强度高、导电和导热性好等特点，广泛应用在电气工业、电子封装及军事工业等领域。由于W和Cu在固态下互不相溶，故在W-Cu复合材料制备时一般需将两者粉末混合后在较高温度下烧结。传统的粉末冶金等工艺在制备形状复杂的薄壁结构零件中存在着诸多问题，新型工艺也由于成本高、效率低等原因而进展缓慢。本研究采用冷喷涂制备了纯铜及W-Cu复合涂层，并对涂层进行不同温度的真空热处理，研究了热处理前后涂层组织结构的变化。通过准静态及动态下对涂层加载的方式，测试了涂层的准静态及动态力学性能，并探讨了热处理对涂层力学性能的影响。在此基础上，利用MATLAB及ABAQUS有限元软件确定出基于涂层真实微观组织的建模方法，，采用计算细观力学方法研究了涂层微观结构与力学性能之间的关系。研究结果表明喷涂气体种类是影响涂层沉积效率、组织结构及性能的主要因素，氦气制备涂层其沉积效率、致密度及W颗粒含量等要高于氮气喷涂涂层；铜涂层热处理后涂层中的铜颗粒界面出现部分融合，同时涂层内部观察到等轴晶粒，W-Cu复合涂层内部的孔隙逐渐消失，从而其致密度逐渐提高。 Cu涂层的力学性能显示，喷涂态涂层内存在显著的加工硬化，氦气喷涂涂层的屈服强度高于氮气喷涂涂层；经400°C热处理1h后，涂层内的加工硬化得以消除，其动态力学性能与块材之间差异主要源于冷喷涂涂层典型的多界面结构。随热处理温度的升高，W-Cu复合涂层在准静态及动态加载下的屈服强度升高，动态加载下涂层屈服强度及最大应变值均明显高于准静态加载。通过MATLAB编程结合ABAQUS软件建立了基于复合涂层真实微观结构的建模方法，所获得的涂层符合真实涂层中两相含量和分布的统计结果。模拟结果显示，W-Cu复合涂层中，作为增强相的W颗粒内有明显的应力集中，部分W颗粒内部有较高的拉应力；采用周期性边界条件模拟获得的应力-应变曲线与400°C热处理涂层实测力学性能符合较好，准静态及动态加载下屈服强度模拟结果与实测结果的误差分别为12.5%和3%，最大应力值模拟结果与实测相比分别相差约16%和5%；图片尺寸对模拟结果影响不大。
[Abstract]:W-Cu composite is widely used in electrical industry, electronic packaging and military industry because of its high strength, good conductivity and good thermal conductivity. Therefore, in the preparation of W-Cu composite materials, it is generally necessary to mix the two powders and then sintered at higher temperature. The traditional powder metallurgy process has many problems in the preparation of thin-walled structural parts with complex shapes, and the new technology is also of high cost. Low efficiency and other causes of slow progress. In this study, pure copper and W-Cu composite coatings were prepared by cold spraying. The microstructure of the coatings was studied by vacuum heat treatment at different temperatures. The coating was loaded under quasi-static and dynamic conditions. The quasi-static and dynamic mechanical properties of the coating were tested, and the effect of heat treatment on the mechanical properties of the coating was discussed. On the basis of this, the modeling method based on the true microstructure of the coating was determined by using MATLAB and ABAQUS finite element software. The relationship between microstructure and mechanical properties of coatings was studied by means of computational meso-mechanical method. The results show that the type of spray gas is the main factor affecting the deposition efficiency, microstructure and properties of the coating. The deposition efficiency, density and W particle content of the coating prepared by helium are higher than those of the coating prepared by nitrogen spraying. After heat treatment, the interface of copper particles in the coating is partially fused, and the pores in the coaxial grain and W-Cu composite coating are observed to disappear gradually, and the density of the composite coating is gradually increased. The mechanical properties of the Cu coating show that there is significant work hardening in the sprayed coating, the yield strength of the helium sprayed coating is higher than that of the nitrogen sprayed coating, and the work hardening in the coating can be eliminated after heat treatment of 400 掳C for 1 h. The difference between dynamic mechanical properties and bulk materials is mainly due to the typical multi-interface structure of cold-sprayed coatings. The yield strength of W-Cu composite coatings increases with the increase of heat treatment temperature under quasi-static and dynamic loading. The yield strength and maximum strain value of the coating under dynamic loading are obviously higher than those under quasi static loading. A modeling method based on the real microstructure of composite coatings was established by MATLAB programming and ABAQUS software. The obtained coating accords with the statistical results of two-phase content and distribution in real coatings. There is obvious stress concentration in W particles as reinforcement phase and high tensile stress in some W particles, and the stress-strain curves obtained by using periodic boundary conditions are in good agreement with the measured mechanical properties of 400 掳C heat treatment coating. Under quasi-static and dynamic loading, the errors of the yield strength simulation results and the measured results are 12.5% and 3, respectively, and the maximum stress simulation results are about 16% and 5 respectively different from the measured ones, and the image size has little effect on the simulation results.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4

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