Ti-22Al-27(Nb,Zr)合金的高温氧化行为（英文）

研究了Ti2Al Nb基合金Ti-22Al-(27-x)Nb-x Zr(x=0,1,6,at%)在650~800℃的氧化行为。采用XRD和SEM等测试技术对此温度区间形成的氧化层特征进行了分析。结果表明,相比Ti-22Al-27Nb,含锆合金具有较好的抗氧化性能。Ti-22Al-(27-x)Nb-x Zr合金在650℃氧化100 h,主要氧化产物为Ti O2,而在800℃氧化100 h,Ti O2,Al2O3和Al Nb O4为主要产物,但是在Ti-22Al-21Nb-6Zr合金中还有Zr O2生成。Ti-22Al-26Nb-1Zr合金具有优异抗氧化性能,归因于氧化产物细化形成了致密的氧化层,而Ti-22Al-21Nb-6Zr合金,虽然在800℃也形成了较多Al2O3,但是氧化层中的Zr O2为氧的快速扩散提供通道,进而导致该合金氧化增重明显。     

High-Temperature Oxidation Behavior of Ti-22Al-27(Nb, Zr) Alloys

研究了Ti2Al Nb基合金Ti-22Al-(27-x)Nb-x Zr(x=0,1,6,at%)在650~800℃的氧化行为。采用XRD和SEM等测试技术对此温度区间形成的氧化层特征进行了分析。结果表明,相比Ti-22Al-27Nb,含锆合金具有较好的抗氧化性能。Ti-22Al-(27-x)Nb-x Zr合金在650℃氧化100 h,主要氧化产物为Ti O2,而在800℃氧化100 h,Ti O2,Al2O3和Al Nb O4为主要产物,但是在Ti-22Al-21Nb-6Zr合金中还有Zr O2生成。Ti-22Al-26Nb-1Zr合金具有优异抗氧化性能,归因于氧化产物细化形成了致密的氧化层,而Ti-22Al-21Nb-6Zr合金,虽然在800℃也形成了较多Al2O3,但是氧化层中的Zr O2为氧的快速扩散提供通道,进而导致该合金氧化增重明显。     

Ti-45Al-8(Nb,Hf,Y)-0.2B合金高温抗氧化性研究

设计了铌当量约为8的三种成分合金：Ti-45Al-8Nb-0.2B,Ti-45Al-4Nb-0.5Hf-0.1Y-0.2B,Ti-45Al-7Nb-0.1Hf-0.1Y-0.2B, (at.%),研究了这三种合金在900℃静止空气中的断续氧化行为。研究结果表明：Hf、Y联合微合金化的合金氧化膜与基体粘附性明显增强;低Nb/Hf比值的Ti-45Al-4Nb-0.4Hf-0.1Y-0.2B的合金氧化增重小、抗氧化性强,高Nb/Hf比值的Ti-45Al-7Nb-0.1Hf-0.1Y-0.2B合金氧化增重大,抗氧化性差。对氧化膜的扫描电镜(SEM)、能谱分析(EDS)及X射线衍射（XRD）分析表明,Hf、Y的联合加入促进了Al2O3膜的须状生长形态,从而提高了氧化膜与基体粘附性,低Nb/Hf比值的合金中形成了较厚的连续致密的Al2O3膜,提高了合金的抗氧化性;高Nb/Hf比值的合金内存在明显的外氧化现象,导致了该合金抗氧化性下降。     

合金元素Nb在TiAl高温氧化行为中的作用

研究了Ti-45Al-10Nb(at%)合金在800℃－960℃氧气和空气中的氧化行为，并与Ti-50Al(at%)合金作一对比，表明该合金具有较好的高温抗氧化性能，其氧化增重速率略优于文献报道的铁基耐热不锈钢，发现了Ti-45Al-10Nb合金在空气中的氧化增重速率明显低于在纯氧中的氧化增重速率，X－射线相分析与能谱分析表明氧化产物主要由TiO2与Al2O3组成，但空气中氧化后的氧化产物中含TiN相，认为它是降低氧化速率的主要原因，并且认为合金元素Nb稳定了氧化层中的TiN相，因而提高了合金在空气中的抗氧化性能。     

Ti-45Al-8(Nb,Hf,Y)-0.2B合金的高温抗氧化性

设计了铌当量约为8at%的3种成分合金:Ti-45Al-8Nb-0.2B,Ti-45Al-4Nb-0.5Hf-0.1Y-0.2B,Ti-45Al-7Nb-0.1Hf-0.1Y-0.2B(at%),研究了这3种合金在900℃静止空气中的断续氧化行为。研究结果表明:Hf、Y联合微合金化的合金氧化膜与基体粘附性明显增强;低Nb/Hf比值的Ti-45Al-4Nb-0.5Hf-0.1Y-0.2B合金的氧化增重小、抗氧化性强,高Nb/Hf比值的Ti-45Al-7Nb-0.1Hf-0.1Y-0.2B合金的氧化增重大,抗氧化性差。对氧化膜的扫描电镜(SEM)、能谱(EDS)及X射线衍射(XRD)分析表明,Hf、Y的联合加入促进了Al2O3膜的须状生长形态,从而提高了氧化膜与基体粘附性,低Nb/Hf比值的合金中形成了较厚的连续致密的Al2O3膜,提高了合金的抗氧化性;高Nb/Hf比值的合金内存在明显的外氧化现象,导致了该合金抗氧化性下降。     

Ti6Al7Nb和Ti6Al4V合金的热氧化行为

在600～900℃温度下,0.5～72 h时间范围内空气气氛下对Ti6Al7Nb进行热氧化,根据增重曲线计算其氧化动力学规律,利用XRD、XPS分析表面氧化层的相组成、成分和价态,并以Ti6Al4V合金做为比照.结果表明,Ti6Al7Nb合金较Ti6Al4V合金抗氧化能力更强.同等氧化条件下,Ti6Al7Nb合金的氧化速率常数(k)更小.对短时间(1 h)氧化的样品的表面分析显示:各合金元素均以最高价态或稳定价态存在,其中Al和V被富集,而Nb则贫化;另外,Ti6Al7Nb合金和Ti6Al4V合金氧化层主要由金红石型TiO2(R-TiO2)组成,Al2O3相仅出现在900 ℃Ti6Al4V合金样品中.     

合金元素Nb和Si对O相合金抗氧化性能的影响

研究了添加(0.3-0.9)Si(原子分数,%,下同)对Ti-24Al-14Nb-3V-0.5Mo合金650℃到800℃的静态和循环等温氧化性能的影响.研究结果表明由于增大了表面氧化膜TiO2+Al2O3的致密度,添加Si元素能显著提高O相合金的抗氧化性能,并深入探讨了Si的影响机制.与一种高Nb含量的Ti-22Al-26Nb合金对比研究发现,在O相合金中最佳抗氧化性能对应的Nb含量是14左右.     

W、B、Y微合金化高铌TiAl基合金高温抗氧化性研究

使用元素W、B、Y对Ti-45Al-8Nb合金进行了微合金化,研究了微合金化后高铌TiAl基合金在900℃静止空气中的断续氧化行为。结果表明,与Ti-45Al-8Nb合金相比,经过0.2B与0.1Y联合微合金化后合金的氧化增重小,氧化膜与基体的粘附性强,抗氧化性明显改善;经过0.2W与0.1Y微合金化后合金氧化增重明显,氧化膜容易脱落,合金抗氧化性下降;经过0.2B、0.2W、0.1Y联合微合金化后合金抗氧化性没有明显变化。对氧化膜进行的扫描电镜(SEM)、能谱分析(EDS)及X射线衍射(XRD)分析表明,联合添加B、Y促进了合金中的连续致密的Al2O3条带的形成,W、Y联合微合金化的合金中靠近基体处未形成连续的Al2O3条带,并且混合层中形成了较厚的低铌含量的TiO2层。W、B、Y联合微合金促进了混合层中富Al2O3层的形成。     

Y对Ti-45Al-6Nb合金组织结构和高温氧化性能的影响

研究了Y对电弧熔炼Ti-45Al-6Nb合金组织结构和高温氧化性能的影响。结果表明,不同Y含量的Ti-45Al-6Nb合金均主要由γ+α_2片层组织、B_2析出相和少量Y_2O_3组成,微量Y对合金的相组成没有明显的影响,但能够显著细化合金的α_2+γ片层组织。高温氧化结果表明,Y能够明显改善Ti-45Al-6Nb合金的高温抗氧化性能,且Y含量为0.3%时效果更优:Ti-45Al-6Nb-0.3Y合金在1 000℃空气中的氧化速率为3.26×10~(-2) mg~2/(cm~4·h),分别是Y含量为0.1%和0.9%时合金氧化速率的41.3%和26.1%,较不含Y合金低约1个数量级。     

Ni-Al涂层对Ti-22Al-26Nb合金抗氧化性能的影响

采用爆炸喷涂技术在Ti-22Al-26Nb(原子分数,％)基体上制备了Ni-68．5Al(原子分数,％)合金涂层,涂层在退火后与基体结合良好．XRD分析表明,退火后涂层主要由β-NiAl以及少量Al3Ti和Al3Nb组成．研究了Ni—Al涂层对Ti-22Al-26Nb合金在800℃静态空气中氧化性能的影响．Ti-22Al-26Nb合金氧化后主要生成了疏松多孔的TiO2,其抗高温氧化性能很差．施加Ni—Al涂层后,高温下生成了一层致密的Al2O3,氧化动力学曲线满足抛物线规律,抗氧化性能显著提高．     

Effect of V and Nb additions on microstructure,properties,and deformability of Ti-45Al-9 (V,Nb,Y) alloy

Ti-45Al-9(V, Nb, Y) alloys with four different x=V/Nb (atomic ratio x = 1, 1.5, 2 and 3.5) have been prepared, and the microstructures, properties and hot deformation behaviors were investigated. SEM, XRD and TEM results showed that Ti-45Al-9(V, Nb, Y) alloys were mainly composed of γ, α 2 , and β phase, and the volume fraction of β phase increased with the increase of the atomic ratio of V/Nb. The alloys were featured with lamellar microstructure with β and γ phases locating at the colony boundaries, and some β precipitates appearing at γ/γ interfaces. It was found that the colony size decreased with the increase of x. The alloys exhibited moderate mechanical properties at room temperature, with a yield strength of over 600 MPa, and fractures showed mainly translamellar character. The alloy with x=3.5 exhibited the best deformability at elevated temperature and that with x=1 had superior oxidation resistance at 800 ℃.     

Effect of enamel coating on long-term oxidation and hot corrosion behavior of Ti-24Al-17Nb-0.5Mo alloys

The effect of enamel coating on long-term isothermal oxidation at 700 ℃ and cyclic oxidation at 800 ℃ in air and hot corrosion resistance of Ti-24Al-17Nb-0. 5Mo in 75% (Na2SO4 K2SO4 ) 25% NaCl (mass fraction) molten mixed salts at 700 ℃ was investigated. The results indicate that Ti-24Al-17Nb-0.5Mo alloy exhibits relatively poor long-term oxidation resistance due to the formation of Al2O3 TiO2 Nb2O5 mixed scales and poor hot corrosion resistance due to the spallation of scales formed in molten (Ns, K)2 SO4 NaCl. Enamel coating can effectively protect Ti-24Al-17Nb-0.5Mo alloy from long-term oxidation at high temperature in air and remarkably improve the hot corrosion resistance of Ti-24Al-17Nb-0. 5Mo alloy, and can act as the barrier to suppress the migration of oxygen and corrosive ions into the substrate.     

Effect of Nb on oxidation behavior of high Nb containing TiAl alloys

The isothermal oxidation behavior of Ti-45Al-8Nb and Ti-52Al-8Nb alloys at 900 °C in air was investigated. The early oxidation behaviors were studied by using XPS and AES. And the microstructure and the composition of the oxidation scale were studied by using XRD and SEM. The results show that the oxidation behavior of TiAl alloy is significantly improved by Nb addition. Nb substitutes for Ti in TiO₂ as a cation with valence 5, and thus to suppress TiO₂ growth. The (Ti,Nb)O₂-rich layer is a dense and chemically uniform which is more protective than the TiO₂ layer. Nb addition also lowers the critical Al content to form an external alumina. Nb₂Al phase is formed in the metallic matrix at the oxide–metal interface on the high Nb containing TiAl alloys.     

反应烧结Ti-22Al-25Nb合金的高温氧化行为

Ti-22Al-25Nb是一种高温结构材料，它的抗氧化性对今后的发展和应用具有重要意义。采用元素粉末和反应烧结法制备了Ti-22Al-25Nb烧结合金，研究了其在静态空气中的氧化行为(923~950℃温度范围内)。不同温度(650 °C, 750 °C, 850 °C, 950 °C)下的最大增重分别为0.15 mg﹒cm-2、0.41 mg·cm-2、1.68 mg·cm-2和6.9 mg·cm-2。研究发现Ti-22Al-25Nb烧结合金具有良好的抗氧化性，特别是在750°C以下（950°C时发生氧化分解）。根据氧化动力学分析，在750℃以下，氧化行为大致遵循抛物线规律，而在850℃以上，氧化行为符合线性规律。讨论了铌合金元素对氧化动力学的影响，通过对氧化形态和相的观察和分析，证明O相（有序Ti2AlNb相）的抗氧化性能优于其它相，其原因可以解释为不同相的Nb含量的差异导致抗氧化性的差异。     

Effects of yttrium on microstructures and properties of Ti- 17Al-27Nb alloy

1 Introduction With the rapid development in aerospace technology, the aero engine components have to endure larger force and higher temperature due to speed increase of aero-craft. Therefore, more requisitions have to be presented when selecting material…     

Effect of Cr, Nb, Mn, V, W and Si on high temperature oxidation of TiAl alloys

Alloys of Ti−(47,51)Al, Ti47Al−4Cr, Ti48Al−2Cr2Nb, Ti47Al−1Mn, Ti39.4Al−10V, Ti48.4Al−1.9W, and Ti43Al−2W0.1Si were oxidized at temperatures between 800 and 1000 °C in air to determine the effect of each alloying element on oxidation behavior. Among the alloys tested, the Ti48.4Al-1.9W alloy displayed the best oxidation resistance, due to the beneficial effects of W, whereas the Ti39.4Al-10V alloy displayed the worst oxidation resistance, due to the formation of volatile V-oxides. Cr was harmful while Nb was beneficial. The oxidation rate of each alloy was not strictly proportional to temperature, because each alloying element had different temperature sensitivity with respect to oxidation rate.     

Comparison of molybdenizing and NiCrA1Y coating on Ti and Ti-6A1-4V

Two surface treatments, molybdenizing and depositing NiCrAIY coating, were applied to improve the microhardness and the oxidation re-sistance of titanium and Ti-6Al-4V. Coupons were analyzed using optical microscopy (OM), scanning electron microscopy (SEM) with X-ray energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). Vickers hardness and isothermal oxidation tests were carded out to evaluate the effects of these two surface treatments on the microhardness and oxidation resistance of the substrates. The post vacuum heat treatment of the NiCrAlY coating and the molybdenizing parameters were also discussed. It is found that molybdenizing can obviously in-crease the surface hardness of titanium due to the formation of β,α", and α' phases in the diffusion layer. As γ' phase is formed after vacuum heat treatment, the NiCrAIY coating is effective in improving the surface hardness of Ti-6Al-4V. The NiCrAlY coating can obviously de-crease the oxidation rate of Ti-6Al-4V at 700-900℃, which can be attributed to the formation of Al2O3 and Cr2O3 mixed scale during the oxidation.     

Oxidation characteristics of Ti3Al-Nb alloys and improvement in the oxidation resistance by pack aluminizing

The oxidation behavior of three T_i3-Al-Nb alloys: Ti-25Al-11Nb, Ti-24Al-20Nb, and Ti-22Al-20Nb was investigated in the temperature range of 700–900°C in air. The uncoated alloy Ti-25Al-11Nb showed the lowest weight gain with nearly parabolic oxidation rate; while the other two alloys had much higher weight gain, accompanied by excessive oxide scale spalling. The scale analysis, using XRD, SEMIEDAX, and AES revealed that the scale was a mixture of TiO₂, Al₂O₃, and Nb₂O₅ with the outer layer rich in TiO₂. The effect of variation in Al and Nb content on the oxidation behavior is discussed. A decrease in Al content of the alloy adversely affects the oxidation resistance; and it seems that a Nb content as high as 20 at.% is also not beneficial. Hence these alloys, especially Ti-24Al-20Nb and Ti-22Al-20Nb, should not be used in the as-received condition above 750°C. An attempt was made to improve the oxidation resistance of these alloys by pack aluminizing which led to the formation of an Al rich TiAl₃ surface layer doped with Nb. The coating process was gaseous-diffusion controlled with a parabolic Al deposition rate. The weight gains for the aluminized alloy specimens oxidized at 900°C in air were much lower than that of the uncoated specimens. The weight gains were further decreased in the case of Si-modified aluminized specimens. The scale analysis revealed an alumina-rich scale with some amount of titania doped with Nb. The improvement in the oxidation resistance of the pack-aluminized alloys at 900°C is attributable to the formation of the alumina-rich oxide scale. The addition of Si to the aluminizing pack seems to promote further the growth of an alumina-rich scale by lowering the oxygen partial pressure in the system.