分类： 材料科学 >> 金属与冶金 提交时间： 2022-09-26 合作期刊: 《桂林电子科技大学学报》
摘要： 采用直流磁控溅射技术,研究不同功率(60、110、150 W)下,在钛合金基材上制备的Ag-TiN陶瓷涂层的微观结构及性能。分别利用扫描电子显微镜、X射线能谱分析和X射线衍射分析涂层表面、截面的形貌与组织成分。采用往复摩擦磨损试验机测试涂层的耐磨损能力。结果表明,在三组功率下试样涂层厚度分别为2.941、3.625、5.023 m,表面Ag的质量分数分别为50.97%、70.42%、91.25%,表面主要物相是Ag、TiN与TiO2;随着功率的增大,涂层表面晶粒体积减小、涂层更加均匀致密;Ag颗粒从涂层中扩散到表面,充当润滑物,降低涂层的摩擦系数,110 W 制备的样品摩擦系数降低31%;在载荷10 N和20 N下磨损试验中,涂层表面磨损量减少33%,耐磨损性能比基体材料分别提高了1.41倍和1.31倍。制备的Ag-TiN涂层有效改善了钛合金表面微观结构,提高了涂层耐磨性能。在110 W 溅射功率下制备的涂层微观组织良好,摩擦系数较低,耐磨性最佳。
分类： 材料科学 >> 材料科学（综合） 分类： 材料科学 >> 金属与冶金 提交时间： 2020-01-07
Xiangyan Li
Yange Zhang
Yichun Xu
Xuebang Wu
Xianping Wang
B.C. Pan
C.S. Liu
Q.F. Fang
Jun-Ling Chen
G.-N. Luo
Zhiguang Wang
X. Liu
摘要： Nano-crystalline metals (NCs) exhibit radiation-tolerance due to the sink of grain boundaries (GBs) for radiation-induced defects such as self-interstitial atoms (SIAs) and vacancies (Vs). However, the relevant mechanisms for the radiation damage accumulation and GB structural relaxation under high radiation field in NCs are still not well understood due to the lack of self-consistent across-scale techniques for simulating radiation-induced microstructures evolution. In this article, by combining coarse-grained and atomistic simulations, we proposed a coupling method to investigate the evolution of the microstructure and SIA/V-GB interaction under cumulative irradiation in NC iron. The SIA overloaded effect was revealed in iron GBs at a high radiation dose rate and/or low temperature. Two types of GB structural response were observed to cumulative irradiation. With the SIA accumulated at the GB, the new GB phase formed and then a critical concentration of the SIA at the GB transited to the small quantity of the V during the GB structural recovery, accompanied by the local GB motion. Consequently, the GB’s role for Vs nearby alternated between the trapping and annihilation center with radiation dose. Alternatively, GB developed to a disordered structure after trapping abundant SIAs. The GB response pattern to cumulative irradiation that is related to the SIA formation energy at the GB or the GB thermal stability is well manifested in the cumulative distribution function of the defects formation energy and its energy level density. The present work reveals the dynamic healing picture for radiation damage near the GB under cumulative irradiation.
分类： 材料科学 >> 金属与冶金 提交时间： 2018-09-14
摘要： 理解合金元素如何调制金属材料的弹性模量在固体物理理论及金属材料的机械性能的工程设计领域都很重要。本文采用第一性原理方法计在合金原子浓度在 0.4 到 1.85 at% 范围内 12 种铁基固溶体的弹性模量并研究合金元素对 bcc 铁基体弹性模量的机制。
分类： 材料科学 >> 金属与冶金 提交时间： 2017-08-23
摘要： Nonuniform strain fields might induce the segregation of alloying solutes and ultimately lead to the mechanical performance degradation of body-centered-cubic (bcc) Fe based steels serving in extreme environments, which is worthy of investigation. In this paper, two typical volume conserving strains, shear strain (SS) and normal strain (NS), are proposed to investigate the strain effects on solute stabilities in bcc iron by first-principles calculations. For solutes in each transition metal group, the calculated substitution energy change due to SS exhibits a linear dependence on the valence d radius of the solutes, and the slope decreases in an exponential manner as a function of the absolute difference between the Watson’s electronegativity of iron and the averaged value of each transition metal group. This regularity is attributed to the Pauli repulsion between the solutes and the nearest neighboring Fe ions modulated by the hybridization of valence d bands and concluded to be originated from the characteristics of valence d bonding between the transition-metal solutes and Fe ions under SS. For main-group and post transition-metal solutes, the considerable drop of substitution energy change due to NS is concluded to be originated from the low-energy side shift of the widened valence s and p bands of the solutes. Our results indicate that the stabilities of substitutional solutes in iron under volume-conserving strain directly correlate with the intrinsic properties of the alloying elements, such as the valence d radius and occupancy, having or not having valence s and p bands.
分类： 材料科学 >> 金属与冶金 提交时间： 2017-08-23
摘要： Under nuclear fusion environments, displacement damage in tungsten (W) is usually caused by neutrons irradiation through producing large quantities of vacancies (Vs) and interstitials (SIAs). These defects not only affect the mechanical properties of W, but also introduce trap sites for implanted hydrogen isotopes and helium. Nano-structured W with high fraction of free surfaces has been developed to mitigate the radiation damage. However, the mechanism of the surface reducing defects accumulation is not well understood. Using multiscale simulation methods, we investigated the interaction of the SIA and V with different surfaces at across length and time scales. We found that, at a typical operation temperature of 1000K, surface (110) preferentially heals radiation damage of W compared with surface (100) and boundary (310). On surface (110), the diffusion barrier for the SIA is only 0.68eV. The annihilation of the SIA-V happens via the coupled motion of the V segregation towards the surface from the bulk and the two dimensional diffusion of the SIA on the surface. Such mechanism makes the surface (110) owe better healing capability. On surface (100), the diffusion energy barrier for the SIA is 2.48eV, higher than the diffusion energy barrier of the V in bulk. The annihilation of the SIA-V occurs via the V segregation and recombination. The SIA was found to migrate one dimensionally along a boundary (310) with a barrier of 0.21eV, leading to a lower healing efficiency in the boundary. This study suggested that the on-surface process plays an important role in healing radiation damage of NP W in addition to surface-enhanced diffusion and annihilation near the surface. A certain surface structure renders nano-structured W more radiation-tolerant.
分类： 材料科学 >> 材料化学 分类： 材料科学 >> 金属与冶金 提交时间： 2017-08-15
摘要： All-vanadium redox flow battery (VRFB) is a large-scale electrochemical energy storage technology with numerous potential applications because of its inherent safety and long service life. In previous years, a novel mixed-acid electrolyte system, vanadium electrolytes with mixture of sulfuric acid and hydrochloric acid, has been developed by the Pacific Northwest National Laboratory (PNNL) to increase vanadium solubility, which can effectively raise the electrolyte energy density from 25 Wh/L to 40 Wh/L. To further improve mixed-acid VRFBs, in present work, high purity mixed-acid electrolytes were prepared using a novel direct dissolution – electrochemical reduction process from high purity vanadium oxytrichloride (VOCl3). And the purity and electrochemical properties were investigated, comparing with common mixed-acid electrolytes and regular sulfate electrolytes prepared from metallurgical grade vanadium pentoxide. It was found that the novel process demonstrated a great potential for the low cost and high efficiency production of high purity electrolytes with excellent electrochemical properties for mixed-acid VRFBs. Comparing the traditional high purity electrolytes preparation process, the present novel method will dramatically cut the cost by more than 90 percent, which will considerably facilitate the commercial application of high performance and high density VRFBs.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 分类： 材料科学 >> 金属与冶金 提交时间： 2017-01-04
摘要： 摘 要 金属材料在服役过程中常因受到环境的影响而造成腐蚀, 从而极大地降低了金属摘 要 金属材料在服役过程中常因受到环境的影响而造成腐蚀, 从而极大地降低了金属的服役寿命, 因此研究金属材料的腐蚀行为具有很强的现实意义. 本文在现有的金属腐蚀理论的基础上, 引入腐蚀电流衰减常数, 利用阻抗电路的暂态过程推导出金属腐蚀电流密度与腐蚀时间的关系, 并分析了温度对点蚀长大的影响, 再通过法拉第公式得到金属点蚀的长大速率和腐蚀深度随时间的变化关系 . 在非平衡统计理论的基础上 , 通过建立和求解Fock-Plank方程推导出点蚀的概率密度分布函数, 并利用最弱链模型计算穿孔概率与可靠性.最后, 以飞机铝合金 LD2 结构材料为例, 计算其点蚀深度、速率及概率密度分布函数, 得出材料在不同腐蚀年限时的最概然点蚀深度值、穿孔概率和可靠性, 期望应用于金属材料的点蚀寿命预测和可靠性分析.
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