共查询到20条相似文献,搜索用时 93 毫秒
1.
采用渗流铸造工艺制备了钨丝增强不同Nb含量的Zr基金属玻璃复合材料,利用X-Ray衍射、扫描电镜以及电子探针考察了复合材料界面反应和界面扩散情况,研究了基体合金中的Nb含量对复合材料界面反应和界面扩散的影响。结果表明:对Zr55Al10Ni5Cu30基复合材料,渗流时,钨丝与液相中的Zr发生界面包晶反应,生成W5Zr3界面相,并使界面位置向液相方向移动。在Zr55Al10Ni5Cu30合金的基础上添加Nb,发现Nb优先在钨丝界面偏聚,降低了Zr在钨丝界面的偏聚和活度,抑制钨丝与液相中的Zr包晶反应的发生,没有生成W5Zr3界面相,界面处只存在简单的扩散层。同时发现Zr元素在钨丝中的扩散系数降低,此时界面位置向钨丝方向移动。 相似文献
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用渗流铸造水淬法制备了φ6mm×50mm的W纤维增强的Zr4125Ti13.75Cu12.5Ni10Be22.5非晶合金复合材料。采用扫描电镜(SEM)分析了相同渗流时间,不同渗流温度复合材料的界面反应形貌,并采用Push-out法测定了界面剪切强度,讨论了界面特征、界面剪切强度与宏观压缩断裂行为之间的关系。结果表明:渗流铸造法制备的W纤维增强Zr41.25Ti13.75Cu12.5Ni10Be22.5非晶合金复合材料明显提高了非晶合金的塑性和断裂强度。复合材料界面结合包括界面扩散和界面反应两个过程。界面反应程度加剧时界面剪切强度增大,复合材料的破坏方式由纵向劈裂转变为剪切破坏。 相似文献
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利用透射电镜(TEM)中的原位拉伸台对纯金属铝及受强度错配双界面约束的纯铝层拉伸过程进行观察。结果表明:纯金属铝拉伸过程中裂端形成微孔洞后即与主裂纹连接,在界面约束条件下,裂端形成微孔后并非立即与主裂纹连通,而是在更前沿位置产生更多的微孔洞,即发生连续孔洞化。拉伸过程中,裂尖钝化与锐化的现象共存,随着中间纯铝层厚度的降低,裂端发射的位错在其周围晶界形成越来越严重的塞积,大大提高了晶界及裂端前沿应力场强度,引起中间纯铝层的脆化。 相似文献
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从扩散焊接头界面微孔实际形貌和分布特征出发,提出了界面微孔周期性分布的二维有限元模型,应用ANSYS电磁场分析模块,考察了界面焊合率、界面微孔宽度和长度对电阻增量的影响.结果表明,扩散连接接头的界面焊合率与电阻增量之间呈双曲线变化规律,界面微孔的宽度和长度对电阻增量均有影响.当界面焊合率在20%~80%范围内时,电阻增量与界面焊合率之间表现出更高的敏感性.基于Lodge等人提出的扩散焊界面焊合率与电阻增量关系式,建立了能够包含界面微孔几何尺寸影响的修正方法. 相似文献
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爆炸焊接铝/不锈钢薄壁复合管界面的微观分析 总被引:3,自引:0,他引:3
采用扫描电镜、能谱仪和显微硬度计对爆炸焊接铝,不锈钢薄壁双金属复合管界面的显微组织、成分和硬度梯度进行了分析研究。结果表明,结合良好的薄壁铝,不锈钢复合管的结合区界面,是平直界面和平直至波形过渡的非稳态波形界面二者混合出现;元素在界面扩散主要是Fe,Cr,Ni元素向Al层内进行扩散,Al元素向不锈钢层内扩散量极少,界面附近不锈钢侧有明显硬化现象;由于热影响消除了铝层硬化现象。在Al侧出现的由超塑流变造成的组织变化,并没有从硬度分布表现出来;需要严格控制爆炸焊接静态参数,尽量减少Al-Fe化合物脆性相生成量。 相似文献
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采用冷压烧结-热挤压复合工艺制备Si C颗粒增强Al-Si基复合材料,利用高分辨电子透射电镜分析该复合材料的界面显微组织。结果表明:制备得到的Si C颗粒增强Al-Si基复合材料存在清晰的波浪形界面结构,且存在较多的扇贝状结构与许多微孔;时效处理使界面的波浪形程度降低,微孔与扇贝状结构消失。时效处理后复合材料界面存在4 nm厚的非晶层,对复合材料进行热挤压会使Al基出现局部熔融现象。热压后复合材料的界面第二相结构和Al基体之间形成了清晰的界面,第二相成分是Al_4Cu_9。在时效处理后复合材料界面区域存在众多的Al_2Cu小尺寸颗粒,并形成了均匀的分布状态,同时发生了明显的晶格畸变。 相似文献
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《中国有色金属学报》2019,(11)
以纳米团聚体Al_2O_3-13%TiO_2(质量分数)复合涂层粉末为原材料,采用激光熔覆工艺在Ni625合金基体表面制备316L微孔结构/Al_2O_3-13%TiO_2复合涂层。通过扫描电镜(SEM)、XRD和线扫描仪分析涂层和微孔粘结层的界面形貌和界面元素的分布状态,研究微孔结构对涂层结合强度的影响。结果表明:界面间结合方式为机械结合;虽然界面之间未发生元素扩散现象,但在微孔粘结层"铆接"作用下,粘结层与陶瓷层间形成良好的结合,与直接激光熔覆Al_2O_3-13%Ti O_2涂层相比,316L微孔结构/Al_2O_3-13%TiO_2复合涂层结合强度较高,提高8.7%;残余应力相对较低,减小13.6%,且表面涂层由α-A1_2O_3、Rutile-TiO_2和Al_2Ti_7O_(15)组成,其中以稳态的α-A1_2O_3相为主要组成相。 相似文献
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依靠离心力使金属熔液渗入到短纤维预制件中,凝固后得到金属基复合材料。在不考虑传热影响的基础上,通过分析离心力场中铝熔液在Al2O3短纤维方形预制件中的渗流情况,研究了铝熔液质量、预制件孔隙率和模具转速对渗透压力的影响,推导出了临界渗透参数关系式,分析了各种条件下满足临界渗透的晟小转速、最小渗铸质量以及最小孔隙率及其相互之间的影响规律。结果表明,针对本研究所用模型,温度确定,铝熔液质量、模具转速以及预制件孔隙率决定着渗透能否发生;随着渗透前沿界面的不断推进,渗铸总压力也在逐渐增大,若起始时刻初始界面能满足临界渗透条件,渗铸过程将维持下去,直至渗透过程结束。 相似文献
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Selection of process parameters has great influence on the quality of a welded connection. Mathematical modelling can be utilized in the optimization and control procedure of parameters. Rather than the well-known effects of main process parameters, this study focuses on the sensitivity analysis of parameters and fine tuning requirements of the parameters for optimum weld bead geometry. Changeable process parameters such as welding current, welding voltage and welding speed are used as design variables. The objective function is formed using width, height and penetration of the weld bead. Experimental part of the study is based on three level factorial design of three process parameters. In order to investigate the effects of input (process) parameters on output parameters, which determine the weld bead geometry, a mathematical model is constructed by using multiple curvilinear regression analysis. After carrying out a sensitivity analysis using developed empirical equations, relative effects of input parameters on output parameters are obtained. Effects of all three design parameters on the bead width and bead height show that even small changes in these parameters play an important role in the quality of welding operation. The results also reveal that the penetration is almost non-sensitive to the variations in voltage and speed. 相似文献
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为了选择无心磨削的最佳工艺参数,通过对其加工原理及工艺参数进行分析,在满足产品技术要求和磨削加工条件等设计约束的前提下,建立磨削工艺参数优化的非线性数学模型。应用MATLAB优化工具箱对工艺参数进行优化计算,得到最佳的工艺参数。优化后的工艺参数使得单位时间内的金属切除率大幅度提高,优化计算的结果验证了此方法的有效性。 相似文献
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Abdoul-Fatah Kanta Ghislain Montavon Michel Vardelle Marie-Pierre Planche Christopher C. Berndt Christian Coddet 《Journal of Thermal Spray Technology》2008,17(3):365-376
The plasma-sprayed coating architecture and in-service properties are derived from an amalgamation of intrinsic and extrinsic
spray parameters. These parameters are interrelated; following mostly non-linear relationships. For example, adjusting power
parameters (to modify particle temperature and velocity upon impact) also implies an adjustment of the feedstock injection
parameters in order to optimize geometric and kinematic parameters. Optimization of the operating parameters is a first step.
Controlling these is a second step and consists of defining unique combinations of parameter sets and maintaining them as
constant during the entire spray process. These unique combinations must be defined with regard to the in-service coating
properties. Several groups of operating parameters control the plasma spray process; namely (i) extrinsic parameters that
can be adjusted directly (e.g., the arc current intensity) and (ii) intrinsic parameters, such as the particle velocity or
its temperature upon impact, that are indirectly adjusted. Artificial intelligence (AI) is a suitable approach to predict
operating parameters to attain required coating characteristics. Artificial Neural Networks (ANN) and Fuzzy Logic (FL) were
implemented to predict in-flight particles characteristics as a function of power process parameters. The so-predicted operating
parameters resulting from both methods were compared. The spray parameters are also predicted as a function of achieving a
specified hardness or a required porosity level. The predicted operating parameters were compared with the predicted in-flight
particle characteristics. The specific case of the deposition of alumina-titania (Al2O3-TiO2, 13% by weight) by APS is considered. 相似文献
14.
The influence of combined laser parameters on in-situ formed TiC morphology during laser cladding 总被引:2,自引:0,他引:2
In this paper, the effect of laser cladding process parameters on TiC morphology is studied. Results show that laser parameters play a crucial role in morphology of TiC. Dendritic or spherical TiC particles with different distribution are observed depending on applied laser parameters. Two combined parameters, effective energy and powder deposition density, are used in order to study the effect of laser process parameters on TiC morphology.A series of experiments are conducted in constant laser power and scan speed, constant effective energy and constant powder deposition density in order to study the TiC morphologies. Results show that both combined parameters and laser parameters should be considered in order to interpret the results. Laser parameters have crucial role in establishing the TiC morphologies by means of temperature and chemical composition.Hardness results of the clad zone depend on morphologies and distributions of TiC particles in the clad. 相似文献
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针对岩体力学参数的未确知性 ,提出了基于证据理论的岩体力学参数信度估计方法。在构造岩体力学参数的识别框架上 ,对多个具有不同信度的抽样试验证据用Dempster Shafer合成法则进行信度综合 ,从而获得在其识别框架上的基本可信度分配、信任函数和似真函数 ,并在此基础上 ,利用定义的类概率函数确定岩体力学参数的取值。应用实例表明 ,该方法在岩体力学参数的分析和选取上取得了较好的结果。 相似文献
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附加参数与基本参数空间关系的度量 总被引:7,自引:0,他引:7
合理地选择参数,避免参数间的强复共线性,是参数有效估计的关键之一。通过将参数X分为两类,即基本参数X1和附加参数X2。并假定附加参数的选取不当是造成参数间强复共线性的主要原因,提出了用点(X2中的一列向量)到空间(由X1所对应的列向量张成Hilbert空间的子空间H0)夹角的正弦值作为度量标准来优选附加参数,给出了该方法的理论论证,并用两个算便对度量方法进行了验证和说明。 相似文献
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K.H.W. Seah M. Rahman X.P. Li X.D. Zhang 《International Journal of Machine Tools and Manufacture》1996,36(12):1385-1400
In recent years, many publications have appeared dealing with chip breaking in orthogonal cutting of metals. However, in industry, oblique cutting and not orthogonal cutting is encountered in almost all actual machining operations. This paper deals with a model of chip flow, chip curl and chip breaking for oblique cutting. To simplify the analysis, a set of equivalent parameters are introduced. The relationship between the machining parameters and their corresponding equivalent parameters is developed theoretically and experimentally. To assess the level of chip breaking, a criterion of chiplbreaking is suggested under the concept of these equivalent parameters. The agreement of the experimental results with the predictive data of the model verifies that the definition of these equivalent parameters is reasonable. The influences of various machining parameters are discussed, in relation to their corresponding parameters. One significant finding is that the effect of each of the machining parameters on chip breaking is not totally inpdependent of one another. This implies that careful attention must be paid to the relationship between various machining parameters in three-dimensional parameters. 相似文献