A thermo-gravimetric and microstructural study of the oxidation of Nbss/Nb5Si3-based in situ composites with Sn addition
A thermo-gravimetric and microstructural study of the oxidation of Nbss/Nb5Si3-based in situ composites with Sn addition
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DOI：
10.1016/j.intermet.2006.06.003
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发表时间：
2007-03-01
期刊：
影响因子：
4.4
通讯作者：
Shao, Guosheng
中科院分区：
文献类型：
--
作者：
Geng, Jie;Tsakiropoulos, Panos;Shao, Guosheng
添加Sn对Nb-24 Ti-18 Si-5Al-5Cr-2 Mo-5 Hf-5Sn（at.%）氧化的影响在800 ℃和1200 ℃下，在静态空气中，使用热重分析和显微组织分析研究了铸态（AC）和热处理（HT）条件下的合金（JG 6）。研究了合金的氧化动力学、氧化膜的形貌和微观结构以及氧化后合金块体的微观结构。氧化通过向内的氧阴离子扩散发生。将JG 6在800 ℃和1200 ℃下的氧化与不含Sn的Nb-Ti-SiCr-Al-Mo-Hf合金的氧化进行比较，并且发现通过添加Sn已经得到改善。在800 ℃下，热处理的Nb-24 Ti-18 Si-5Al-5Cr-2 Mo-5 Hf合金（JG 4-HT）所表现出的有害氧化通过与5at.% SN.在800 ℃下消除疲劳归因于合金中Nb固溶体的性质，该固溶体由富Sn、富Si和贫Ti的固溶体组成，通常被贫Sn、贫Si和富Ti的固溶体包围。在1200 ℃下在JG 6上形成的氧化皮没有与基底金属分离，并且由Nb 2 O 5、TiO 2、SiO2、HfO 2和TiNb 2 O 7组成。在合金JG 6-AC和JG 6-HT在1200 ℃下氧化后，在扩散区中形成TiN（而不是TiO 2）和（Nb，Ti）（5）（Sn 1-xSix）（3）相（其被认为是基于Nb 5Sn 2Si的三元相）。氧化合金JG 6-AC和JG 6-HT中这些相的形成控制了氧渗透到基材中。与JG 6-HT相比，JG 6-AC在1200 ℃下的更好的氧化性能归因于在前者中形成Nb 3Sn。这表明，在微观结构中存在的Sn-贫，Si-贫和Ti-富Nb，是在氧化的JG 6-AC中在1200 ℃氧化的氧化皮/扩散区界面处形成Nb 3Sn相的关键。(c)2006爱思唯尔有限公司保留所有权利。
The effect of Sn addition on the oxidation of the Nb-24Ti-18Si-5Al-5Cr-2Mo-5Hf-5Sn (at.%) alloy (JG6) in the as cast (AC) and heat treated (HT) conditions was studied at 800 degrees C and 1200 degrees C in static air using thermo-gravimetry and microstructural analysis. The oxidation kinetics, morphology and microstructure of the oxide scale and the microstructure of the bulk of the oxidised alloy were investigated. Oxidation occurred by inward oxygen anion diffusion. The oxidation of JG6 at 800 degrees C and 1200 degrees C is compared with the oxidation of Sn-free Nb-Ti-SiCr-Al-Mo-Hf alloys and is found to have been improved by the addition of Sn. At 800 degrees C pest oxidation, which was exhibited by the heat treated Nb-24Ti-18Si-5Al-5Cr-2Mo-5Hf alloy (JG4-HT), was eliminated by alloying with 5 at.% Sn. The elimination of pesting at 800 degrees C is attributed to the nature of the Nb solid solution in the alloy which consists of Sn-rich, Si-rich and Ti lean solid solution usually surrounded by Sn-poor, Si-poor and Ti-rich solid solution. The oxide scales that formed at 1200 degrees C on JG6 did not separate from the base metal and consisted of Nb2O5, TiO2, SiO2, HfO2 and TiNb2O7. TiN, instead of TiO2, and the (Nb,Ti)(5)(Sn1-xSix)(3) phase, which is considered as a ternary phase based on Nb5Sn2Si, are formed in the diffusion zone of the alloys JG6-AC and JG6-HT after oxidation at 1200 degrees C. The formation of these phases in the oxidised alloys JG6-AC and JG6-HT controlled the penetration of oxygen into the base material. The better oxidation performance of JG6-AC compared to JG6-HT at 1200 degrees C is attributed to the formation of Nb3Sn in the former. It is suggested that the presence of the Sn-poor, Si-poor and Ti-rich Nb,, in the microstructure is a key to the formation of the Nb3Sn phase at the scale/diffusion zone inter-face in the JG6-AC oxidised at 1200 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.