Metals and Materials International ( IF 3.3 ) Pub Date : 2021-09-16 , DOI: 10.1007/s12540-021-01047-x Arman Ahmadi-Binahri 1 , Mandana Adeli 1 , M. Reza Aboutalebi 1 , Sergey Krasikov 2
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Abstract
In this study, the application of thermite reactions in Nb2O5–Al system in the fabrication of novel NbAl3/Al2O3 composites was investigated. Combining the thermite reactions with self-propagating high-temperature synthesis (SHS) technique in compressed powder mixtures of Nb2O5 + Al resulted in layer-by-layer progress of the exothermic reaction, controlled formation of the desired products and their coexistence in each reacted layer. Characterization of the products using X-ray diffraction (XRD), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) techniques showed that all samples were composed of a metallic matrix including NbAl3 as the main compound, along with Al2O3 as ceramic reinforcing phase. Differential thermal analysis (DTA) analysis was used to study the mechanism of reaction using both stoichiometric and over-stoichiometric amounts of aluminum. The effect of such parameters as stoichiometry and green density of the samples on the combustion temperature, formed phases, microstructure, and hardness of the obtained composites was investigated using samples with stoichiometric as well 20 wt% and 40 wt% excess aluminum, and samples with green densities of 75%, 85%, and 95% of theoretical maximum density (TMD). The presence of excess aluminum resulted in prolonged reaction times, lower combustion temperatures, and lower mean values of hardness. While the variations in green density had no remarkable effect on the microstructural features of products within the density range under study, the most intensive reactions, highest combustion temperature, and highest mean value of hardness were encountered in samples with green density of 85%TMD.
Graphical Abstract
中文翻译：
铝热剂反应在先进金属间基复合材料生产中的实施：以 Nb2O5/Al 铝热剂混合物为例
摘要
在本研究中，研究了铝热剂反应在 Nb 2 O 5 -Al 体系中在制备新型 NbAl 3 /Al 2 O 3复合材料中的应用。在 Nb 2 O 5 + Al 的压缩粉末混合物中将铝热反应与自蔓延高温合成 (SHS) 技术相结合，导致放热反应逐层进行，所需产物的受控形成及其共存每个反应层。使用 X 射线衍射 (XRD)、扫描电子显微镜和能量色散 X 射线光谱 (SEM-EDS) 技术表征产品表明，所有样品均由金属基体组成，包括 NbAl3作为主要化合物，以及 Al 2 O 3作为陶瓷增强相。差热分析 (DTA) 分析用于研究使用化学计量和超化学计量铝的反应机理。使用具有化学计量以及 20 wt% 和 40 wt% 过量铝的样品，研究了样品的化学计量和生坯密度等参数对所得复合材料的燃烧温度、形成相、微观结构和硬度的影响。理论最大密度 (TMD) 的 75%、85% 和 95% 的绿色密度。过量铝的存在导致反应时间延长、燃烧温度降低和硬度平均值降低。而在所研究的密度范围内，生坯密度的变化对产品的微观结构特征没有显着影响，
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