渗硅TiAl基合金的氧化动力学

改善TiAl基合金的高温抗氧化性能可更大限度地发挥其性能优势,固体渗硅是一种工艺简便且行之有效的方法,深入了解渗硅TiAl基合金的氧化动力学对保证其安全应用以及进一步的理论和实验研究具有重要意义。对经不同温度、时间固体渗硅处理的TiAl基合金在90 0℃下长期循环氧化过程中的动力学研究表明,其氧化过程通常包含三个阶段,即抛物线、线性和二次氧化阶段。提高渗硅温度有利于提高抗氧化性能。其中,经1 2 5 0℃渗硅2h的试样表现出优异抗高温氧化性能,在所测试的1 0 0 0h以内的整个循环氧化过程中仅出现抛物线氧化阶段,经90 0℃氧化1 0 0 0h后,增重小于0 . 3mg·cm- 2 ,相应的抛物线型氧化速率常数,Kp≈6 . 0 3×1 0 - 5mg2 (cm4 ·h) ,优异的抗氧化性能与其表层形成致密的Al2 O3层和相对稳定的Ti5Si3层有关。     

Cr对TiAl金属间化合物高温氧化性能的影响

研究了Ｔｉ－５０Ａｌ，Ｔｉ－４５Ａｌ－１０Ｃｒ和Ｔｉ－５０Ａｌ－１０Ｃｒ（原子分数，％）合金在８００－１１００℃下的高温氧化性能。结果表明，Ｔｉ－４５Ａｌ－１０Ｃｒ合金在８００和９００℃形成的氧化膜具有与ＴｉＡｌ合金同样的分层结构，外层为ＴｉＯ２，内层为ＴｉＯ２和Ａｌ２Ｏ３的混合氧化物，在内外氧化层中间有一富Ａｌ２Ｏ３４的中间层，但内氧化层中有大量Ｃｒ掺杂，其氧化增重比Ｔｉ－５０Ａｌ的大，而１００     

TiAl基合金的氧化分层

用SEM及EDS研究了5种TiAl基合金经8001－1000℃,100h断续氧化及循环氧化后氧化剖面的结构、组成。结果显示,TiAl氧化表面存在分层现象。首先形成（TiO2 Al2O3）混合层,其次是新相过渡层;较少观察到连续的Al2O3层。因应力作用,氧化层开裂用至剥离后,化学分层转入物理分层阶段,氧化层保护性恶化。     

TiAl合金微弧氧化陶瓷层研究

TiAl金属间化合物具有高的比强度和比刚度，是制造新一代先进航空航天器装置最理想的候选结构材料之一。然而．金属间化合物所面临的主要障碍是其室温塑性低和在高温腐蚀环境中易氧化等问题。微弧氧化是一种在有色金属表面原位生长陶瓷层的新技术。不同     

MCrAlY涂层对TiAl金属间化合物抗高温氧化性能的影响

研究了溅射Ｃｏ－３０Ｃｒ－６Ａｌ－０．５Ｙ及Ｎｉ－３０Ｃｒ－６Ａｌ－０．５Ｙ涂层对ＴｉＡｌ金属间化合物抗高温氧化性能的影响。结果表明，在９００℃－１０００℃范围内，ＣｏＣｒＡｌＹ，ＮｉＣｒＡｌＹ涂层表面由于可形成粘附性良好的Ａｌ２Ｏ３膜。大大改善了ＴｉＡｌ金属间化合物的抗氧化性能。     

TiAl基合金高温氧化动力学分析

关于ｉＡｌ的高温氧化问题，国内外已有广泛报道［１，２］，但缺乏对氧化产物的系统分析．本文从氧化物生成热力学角度讨论了二元ＴｉＡｌ及三元ＴｉＡｌ－Ｃｒ合金氧化产物的生成趋势，旨在为ＴｉＡｌ氧化层构造研究提供理论基础．１ＴｉＡｌ氧化物的热力学计算 二元ＴｉＡｌ在９７３Ｋ以上高温氧化时，生成两种稳定的氧化物［３］：Ｒ－ＴｉＯ２和α－Ａｌ２Ｏ３。由于ＴｉＯ２与Ａｌ２Ｏ３的生成自由能相近［４］，在原子比约为 １：１的 ＴｉＡｌ基合金中，将几乎同时生成两种氧化物，故不能形成单一致密的Ａｌ２Ｏ３保护层． 式中：气…     

制备过程对Ti-48Al-1Cr高温氧化行为的影响

研究了铸造、热压力加工、热处理等制备过程对Ti48Al1Cr合金在900℃静止空气中断续氧化行为的影响。结果表明,不同状态下的氧化规律相似,均介于抛物线与直线之间,幂指数15≤n≤18。100h氧化后,表面形貌均呈现疏松多孔特征;制备过程对试验合金900℃×100h断续氧化行为影响不大。     

EFFECT OF NANOCRYSTALLIZATION ON OXIDATION RESISTANCE OF TiAl INTERMETALLIC COMPOUND

ＥＦＦＥＣＴＯＦＮＡＮＯＣＲＹＳＴＡＬＬＩＺＡＴＩＯＮＯＮＯＸＩＤＡＴＩＯＮＲＥＳＩＳＴＡＮＣＥＯＦＴｉＡｌＩＮＴＥＲＭＥＴＡＬＬＩＣＣＯＭＰＯＵＮＤ①ＴａｎｇＺｈａｏｌｉｎ，ＷａｎｇＦｕｈｕｉ，ＷｕＷｅｉｔａｏＮａｔｉｏｎａｌＫｅｙＬａｂｏｒａｔｏ...     

Effect of Ternary Elements on the Oxidation Behavior of Aluminized TiAl Alloys

The effects of ternary elements added to TiAl on the coating layer formed by the pack-aluminizing process was studied with respect to oxidation resistance and mechanical properties. All the TiAl specimens, with various amounts of Nb, Cr, Fe, and V, were pack aluminized under identical conditions using a high-activity process. Among the ternary alloying elements tested, Nb showed the best property of the TiAl₃ coating layer formed on the surface and, consequently, the best oxidation resistance. The TiAl₃ coating layer becomes thicker and has a finer grain size as the content of Nb or Cr is increased. Microhardness tests revealed that the addition of Nb or Cr improved the toughness of the coating layer and thus improved the cracking resistance. Cyclic oxidation tests showed that the TiAl₃ coating layer formed on the TiAl alloy has better oxidation resistance with increasing Nb content. The ductility and oxidation resistance of the TiAl₃ coating layers improved with Nb addition, which contributes to the grain refinement of TiAl₃. The Nb present in the TiAl₃ coating layer inhibits grain growth by the solute-drag effect and retards inward diffusion of Al to the TiAl matrix by forming (Nb, Ti)Al₃ precipitates during high-temperature oxidation.     

组织结构对片层TiAl合金氧化行为影响

以Ti-48Al-2Cr-2Nb(at%)合金为研究对象,通过热处理获得近片层和全片层两种显微组织,并在800℃空气条件下,进行了100 h的抗氧化性实验。利用OM、SEM、TEM、XRD和EDS对试样的微观结构、相组成及微区成分进行了分析。恒温氧化动力学结果表明:在800℃空气条件下,对于近片层和全片层两种Ti Al合金组织,其恒温氧化动力学曲线符合近抛物线规律,且近片层组织合金的抗氧化性能优于全片层组织。基于氧化动力学曲线、组织结构、氧化膜结构、氧化表面形貌分析,表明Ti Al合金的片层组织结构对其氧化行为具有不可忽视的影响。     

Effect of chromium on the oxidation resistance of TiAl intermetallics

The effect of 10 at.%Cr on the oxidation resistance of TiAl intermetallic compound at 800–1100°C in air was investigated. The results indicated that 10 at.%Cr equally substituting for Ti and Al in TiAl alloy had duplex effects on the isothermal kinetics of DAL At lower temperatures (800–900°C), Cr increased the oxidation rates as a result of the doping effect of Cr in the scale and at higher temperatures (1000–1100°C), especially at 1100°C, Cr significantly reduced the oxidation rates as a result of the formation of a continuous Al₂O₃ film on the surface. 10 at.%Cr only substituting for Ti in TiAl alloy remarkably reduced the oxidation rates at all temperatures by about two orders of magnitude. Moreover, 10 at%Cr significantly improved the cyclic-oxidation rsistance of TiAl alloy.     

Effect of Fe on the high temperature oxidation of TiAl alloys

An alloy of 51.23Ti−48.73Al−0.4Fe (at.%) was oxidized at 800, 900 and 1000°C in air to determine the effect of Fe on oxidation. The scales formed consisted of an outer TiO₂ layer, an intermediate Al₂O₃ layer, and an inner mixed (TiO₂ Al₂O₃) layer, typical of conventional TiAl alloys. A small amount of dissolved Fe ions was weakly segregated in the outer TiO₂ layer and also in the inner (TiO₂−Al₂O₃) mixed layer. Ti₂AIN and TiN were detected in the scale in some instances. A thin, oxygen-affected Ti₃Al sublayer formed at the oxide-substrate interface. The overall oxidation kinetics and the scale morphology were not affected by Fe-addition.     

XRD Investigations of the Phosphorus Effect on the Oxidation of TiAl Alloys by High-Resolution Methods

Recently it has been found that very small amounts (a few 100 ppm) of Padded to -titanium aluminide can significantly alter the oxidationbehavior between 973 and 1273 K. The mechanism responsible for this changeis, however, still not clear. In the present study, phosphorus wasincorporated into the surface of TiAl (containing 50 at.% Al) by ionimplantation and oxidation tests were carried out at 1173 K inair. Improvement of oxidation resistance is only temporary up to 100 hr forphosphorus-implanted TiAl. After 100 hr, the oxidation rate increases andbreakaway oxidation follows. XRD and EPMA showed that the breakawayoxidation is connected with massive nitride formation. Two different modelsare proposed which can explain the effect of phosphorus additions on theoxidation kinetics of TiAl during the protective stage within the first100 hr. The breakaway effect can be explained by penetration of air to themetal–oxide interface zone because of microcrack formation in theoxide scale, which was experimentally proved by acoustic-emission analysis.     

TiAl合金表面高温抗氧化性工艺技术研究现状

TiAl合金由于其密度低,比强度和比刚度高,是航空、航天工业理想的新型高温结构材料.但温度超过800℃.其高温抗氧化性不足已严重影响其实际广泛应用,如何提高TiAl合金的高温抗氧化性已成为普遍关注的问题.本文综述了当今国内、外TiAl合金高温抗氧化性工艺技术的研究现状,重点介绍了表面合金化工艺技术和表面防护涂层工艺技术及其发展趋势.     

钛铝高温氧化表面分析

将５种铸态ＴｉＡｌ置于７００℃～１０００℃静止空气中断续氧化１００ｈ。采用ＸＲＤ和ＳＥＭ／ＥＤＳ分析技术,观察分析了ＴｉＡｌ氧化后的表面形貌、相组成及分布状况,结果表明：氧化产物主要为金红石型Ｒ－Ｔ和刚玉型α－Ａ１２Ｏ３;低温、短时氧化时,氧化产物呈混合形式存在;高温、长时化时,在混合氧化物之外易形成纯Ｒ－ＴｉＯ２晶体层。