W-Nb合金价电子结构参数统计值计算及组织性能研究

发布时间：2018-03-03 17:41

本文选题：价电子　切入点：参数统计值　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：根据固体与分子经验电子理论结合平均原子模型,计算不同Nb含量的W-Nb固溶合金价电子结构参数统计值,计算了合金最强健上共价电子对数的统计值SnA,键能统计值SEA,并得到固溶强化系数S,固溶合金强度因子(η)和硬度(SnA),分析了W-Nb合金成分的性能与价电子结构参数统计值之间的关系。在价电子计算的基础上设计了不同成分的W-Nb固溶合金的实验方案,并利用X射线衍射仪(XRD)、扫描电镜(SEM)、金相显微镜和能谱仪对烧结的合金试样的组织和性能进行表征,研究了加入不同含量的Nb元素对W-Nb固溶合金组织和性能的影响。利用平均原子模型和键距差(BLD)法,采用价电子结构参数统计值结合计算机编程对W-Nb固溶合金价电子结构进行计算,用价电子结构参数的统计值来讨论宏观物理量是合适的。计算了合金的强度因子η、最强键上共价电子数SnA、固溶强化系数S,结果表明,随着Nb含量的增加,SnA、η增大,固溶合金的硬度和强度增加,同时固溶强化系数S随之增加,合金固溶强化效果增强。随着Nb含量的增加,W-Nb固溶合金键能不断增大,但增大的幅度不明显。通过机械合金化方法制备W-Nb合金粉末,并经过放电等离子烧结制备合金试样,结果表明,通过XRD可以看出Nb已经完全固溶到W中去了,Nb含量增加时,衍射峰向低角度偏移。对合金的金相组织和断口形貌进行分析表明,当Nb含量增加时,晶粒尺寸是逐渐由10um减小到3um左右,且致密度也逐渐增大,并且硬度也随之增大,说明Nb的加入可以细化晶粒,提高合金的硬度,这和价电子计算结果基本相似。通过对W-Nb合金的断口形貌进行分析可以看出,W和Nb分布比较均匀,没有出现偏聚现象,并且随着Nb含量的增加,合金的断口中出现螺旋状台阶,使合金的塑性增强。
[Abstract]:Based on the empirical electron theory of solids and molecules combined with the average atomic model, the valence electron structure parameters of W-Nb solid solution alloys with different NB contents were calculated. The statistical values of the logarithm of the strongest covalent electrons, SEAA and the statistical value of bond energy were calculated, and the solid solution strengthening coefficient S, the strength factor (畏) and the hardness of the alloy were obtained. The properties and valence electron structure parameters of W-Nb alloy were analyzed. The experimental scheme of W-Nb solid solution alloy with different composition was designed on the basis of valence electron calculation. The microstructure and properties of sintered alloy samples were characterized by X-ray diffractometer, SEM, SEM, SEM and EDS. The effect of different contents of NB elements on the microstructure and properties of W-Nb solid solution alloy was studied. The average atomic model and bond distance difference (BLDD) method were used to determine the structure and properties of W-Nb solid solution alloy. The valence electron structure of W-Nb solid solution alloy was calculated by using the statistical value of valence electron structure parameters and computer programming. It is appropriate to discuss macroscopic physical quantities with the statistical value of valence electron structure parameters. The strength factor 畏, the covalent electron number SnA on the strongest bond, and the solid solution strengthening coefficient S are calculated. The results show that with the increase of NB content, Sno, 畏 increase. The hardness and strength of the solid solution alloy increase, and the strengthening coefficient S increases, and the solution strengthening effect of the alloy increases. With the increase of NB content, the bond energy of the W-Nb alloy increases continuously. But the increase was not obvious. W-Nb alloy powder was prepared by mechanical alloying and the alloy sample was prepared by spark plasma sintering. The results show that NB has been completely dissolved into W by XRD. The diffraction peak shifted to low angle. The microstructure and fracture morphology of the alloy were analyzed. When NB content increased, the grain size gradually decreased from 10um to 3um, and the density and hardness increased gradually. The addition of NB can refine the grain and improve the hardness of the alloy, which is similar to the results of valence electron calculation. By analyzing the fracture morphology of W-Nb alloy, it can be seen that the distribution of W and NB is relatively uniform and there is no segregation phenomenon. With the increase of NB content, spiral steps appear in the fracture surface of the alloy, which enhances the plasticity of the alloy.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.411

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