TiAl合金的制备及应用现状

TiAl合金密度小、高温性能优异,自20世纪50年代以来已发展到第三代。介绍了TiAl合金的性能特点、发展历程,真空感应熔炼、真空自耗电弧熔炼、等离子冷床炉熔炼等熔炼TiAl合金方法的优缺点,以及国内外TiAl合金的制备情况;提出TiAl合金熔炼过程中存在的问题主要是宏观与微观偏析,应从原料加入方式、原料纯度及熔炼工艺等方面进行改进;此外,对TiAl合金在航空航天、汽车工业等领域的应用现状进行了概括,指出TiAl合金近期的研究重点是大尺寸铸锭的均匀化控制。     

TiAl合金叶片铸造成形工艺研究

采用熔模精密铸造工艺制造TiAl合金叶片,通过对浇注系统设计、型壳制备工艺、熔炼浇注工艺的研究,实现了TiAl合金叶片完整成型。结果表明,合理设计浇注系统和型壳制备工艺可以减少集中缩孔、夹杂和气孔。     

添加钨对TiAI抗氧化性能的影响

住友金属工业公司的穴田博之等人通过在TiAl合金中适当添加钨的试验,证明了钨可改善TiAl合金的抗氧化性能,同时,探讨了含钨的TiAl合金表面抗氧化机理。 试验采用Ti-34.5wt％Al,钨添加量为(1～6)wt％。为了便于比较,还制备了不加钨的Ti-34.5Al二元合金。制备合金的原料选用海绵钛、板状或箔状铝和钨粉。熔炼是在非自耗式钨电极熔炼炉中进行的,经三次熔炼制成120g重的合金锭。在真空     

带缺口的熔模铸造TiAl合金断裂特性的扫描电镜原位观察(英文)

采用感应凝壳熔炼技术和熔模铸造方法制备TiAl合金。在增量加载情况下,采用扫描电镜原位观察技术观察带缺口的熔模铸造TiAl合金试样的裂纹扩展和断裂特性。在拉伸变形的整个过程中,观察并分析裂纹萌生、扩展直至断裂的全过程。结果表明,TiAl合金的断裂机制不仅对于缺口区域附近的微裂纹敏感,而且与层片方向和加载轴的位向有关。当局部应力大于TiAl合金的断裂韧性时,高的拉伸应力就会导致裂纹萌生、扩展直至断裂失效。因此,TiAl合金的塑性和高的拉伸应力导致带缺口的TiAl合金的断裂失效。     

BaZrO_3耐火材料与TiAl合金熔体的界面反应

以自合成的BaZrO3粉体为材料制备成坩埚,在真空条件下熔炼了TiAl合金,并对熔炼后合金的显微组织及合金与BaZrO3耐火材料的界面反应情况进行研究。结果表明:熔炼后合金的显微组织由大量不同取向的片层状α2+γ和少量条块状的γ相组成;合金熔体对BaZrO3耐火材料的润湿性较差,熔炼后未观察到界面反应层的存在;BaZrO3对合金熔体具有良好的化学惰性,是极具潜力的TiAl合金熔炼用耐火材料。     

TiAl预合金粉末的表征和后续致密化显微组织特点

采用感应熔炼气体雾化法制备了TiAl预合金粉末.粉末粒度主要分布在100-250 μm,呈正态分布,粉末平均粒度为120.7 μm.TiAl预合金粉末的相组成与粒度分布有关,γ相所占比例越高,预合金粉末粒度越大.小粒度的预合金粉末主要由α2相组成;预合金粉末在温度高于500℃时效处理,发生α2→γ转变.TiAl预合金粉...     

稀土Y在γ-TiAl基合金及其精密热成形中应用的研究进展

TiAl合金作为新型轻质高温结构材料,其熔炼及制备技术难度大、铸态组织较粗大、室温塑性较低和高温抗氧化能力的不足成为限制其应用的关键。从材料制备成形和合金成分两个角度综述稀土元素Y在TiAl基合金中应用的研究进展,总结国内外对Y_2O_3陶瓷坩埚和型壳面层在TiAl合金熔炼和精密铸造及制备成形过程中的研究进展;阐述稀土元素Y在合金中的形态与分布及其对合金铸态组织的细化及作用机理,并分析Y对合金室温力学性能和抗氧化性能的影响,对Y在TiAl基合金中的进一步研究应用提出建议。     

Nb、Mo对TiAl基合金高温氧化行为的协同效应研究

采用冷坩埚悬浮熔炼技术制备Nb、Mo合金化的TiAl基合金,研究合金在大气环境中的高温长时氧化行为。采用X射线衍射、扫描电镜及能谱分析研究氧化层的相结构、显微组织及与基体合金的界面特征,结合氧化动力学测试研究Nb、Mo对TiAl基合金高温抗氧化行为的协同效应。结果发现,Nb、Mo协同作用较单一元素合金化的TiAl合金具有更为优良的高温抗氧化性,连续致密且与基体良好结合的氧化膜可明显降低合金的氧化速率、减小氧化增重。Nb、Mo掺杂的TiAl基合金氧化层可阻止氧原子向内扩散,Nb、Mo的协同效应有助于改善TiAl基合金的高温抗氧化性。     

TiAl合金增压器涡轮的铸造

采用高频感应加热快速熔炼、低模壳温度稳速浇注工艺铸造出一批TiAl增压器涡轮。TiAl合金由于其比重小，可大大减小涡轮的转动惯量矩，对优化涡轮设计，提高了车辆机动性能有着很重要的意义。     

TiAl合金薄壁环形件精铸成形工艺研究

针对TiAl合金室温塑性低、制备过程容易开裂等问题,采用氧化物陶瓷型壳、真空自耗凝壳熔炼和离心浇注相结合的方式,研究了Ti-48Al-2Cr-2Nb合金的精密铸造成形技术。通过浇注系统设计和浇注工艺优化,采用离心浇注成功制备出TiAl合金环形铸件,直径达260mm,80%区域壁厚在1.5~3.0mm,经无损检测发现铸件无裂纹、缩孔缺陷。     

Laser cladding of titanium alloy coating on titanium aluminide alloy substrate

1　INTRODUCTIONInthedesignandmanufactureofaviationindus try ,differentpartsoftheaircraftengineshouldmeetthedifferentrequirementsonoperatingtemperatureandserviceperformance .Thesoundbondofdissimi laralloysisthekeytechniquefordevelopingnovele quipmentsandimprovingtheirintegralperformance .Lowdensityandexcellenthigh temperaturepropertiesofTiAlalloysmakethem promisinghigh temperaturestructuralmaterials .Successfuljoiningofthesematerialswillincreasetheirutilityinengineer ing[1,2 ] .Somejoinin…     

Research progress on refractory composition and deformability of shell molds for TiAl alloy castings

At present, most TiAl components are produced by an investment casting process. Environmental and economic pressures have, however, resulted in a need for the industry to improve the current casting quality, reduce manufacturing costs and explore new markets for the process. Currently, the main problems for investment casting of TiAl alloys are cracks, porosities, and surface defects. To solve these problems, many studies have been conducted around the world, and it is found that casting defects can be reduced by improving composition and properties of the shell molds. It is important to make a summary for the related research progress for quality improvement of TiAl castings. So, the development on refractory composition of shell molds for TiAl alloy investment castings was reviewed, and research progress on deformability of shell mold for TiAl alloy castings both at home and abroad in recent years was introduced. The existing methods for deformability characterization and methods for improving the deformability of shell molds were summarized and discussed. The updated advancement in numerical simulation of TiAl alloy investment casting was presented, showing the necessity for considering the deformability of shell mold during simulation. Finally, possible research points for future studies on deformability of shell mold for TiAl alloy investment casting were proposed.     

Effects of can parameters on canned-forging process of TiAl base alloy(Ⅰ)--Microstructural analyses

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｉＡｌｂａｓｅｄａｌｌｏｙｈａｓｌｏｎｇｂｅｅｎｃｏｎｓｉｄｅｒｅｄａｓａｐｒｏｍｉｓｉｎｇｍａｔｅｒｉａｌｆｏｒｈｉｇｈｔｅｍｐｅｒａｔｕｒｅａｐｐｌｉｃａｔｉｏｎ ,ｄｕｅｔｏｉｔｓｅｘｃｅｌｌｅｎｔｈｉｇｈｔｅｍｐｅｒａｔ     

Modeling of titanium aluminides turbo-charger casting

The castability of titanium aluminide (TiAl) turbo-charger was investigated with various casting parameters. The fluidity of TiAl alloys increased with mold preheating temperature and centrifugal force. The thermo-physical variables estimated by casting process were applied to the modeling of TiAl turbo-charger casting using the Magmasoft^®. In the case of real casting process, there were many misruns and cold-shuts due to low fluidity of molten TiAl alloy. However, in the modeling, molten TiAl alloys never stop even though the turbo-charger has both the curvature and thin wall parts. Therefore, there were no major defects such as misruns and cold-shuts in the modeling process. The gap between casting and modeling remains in TiAl alloy turbo-charger casting since the modeling process cannot explain the microstructural evolution during solidification and metal–mold reaction between mold materials and TiAl alloy.     

TiAl合金与GH3039高温合金的摩擦焊接

对TiAl合金与GH3039高温合金异种材料进行了摩擦焊接工艺试验. 基于接头的拉伸性能,初步优化了焊接工艺参数. 采用扫描电子显微镜(SEM)和透射电子显微镜(TEM)对焊接接头组织、焊合区成分变化及接头连接机理进行了分析. 结果表明,TiAl合金与GH3039高温合金两种异种材料摩擦焊接具有可行性,在摩擦焊接过程中热力耦合的作用下,GH3039侧热力影响区塑性变形较大,TiAl合金侧热力影响区变形较小;TiAl合金与GH3039高温合金摩擦焊接连接界面两侧的合金元素发生了扩散,形成了复杂的层状金属间化合物组织结构;断于TiAl合金母材的焊接接头断口属于典型的脆性断口.     

TiAl合金冷却相变研究进展及细晶组织调控

TiAl合金是目前航空航天轻质高温结构的热点材料,其最终显微组织很大程度上决定于其冷却过程。由于TiAl合金相图和相变的复杂性,通过冷却过程控制,获得细晶组织结构成为关注的重要问题。综述了TiAl合金冷却相变的研究成果,并给出了关于Ti-48Al-4Nb-2Cr合金相关的进展:首先介绍了TiAl合金的凝固路径与相变行为,然后分别分析了连续冷却转变(CCT)和等温冷却转变(TTT)行为。进一步建立了Ti-48Al-4Nb-2Cr合金CCT图,并指导获得了一种细晶近片层组织。     

TiAl基合金叶片吸铸成形缺陷的数值模拟

采用有限元软件ProCAST模拟TiAl基合金液在金属型真空吸铸成形铸造工艺中的充型凝固过程,分析在充型凝固过程中产生缺陷的原因,并进行了相关的实验验证。在模拟过程中发现铸件中确实存在模拟预测的缺陷,且缺陷主要集中在叶片隼部,在叶身部位出现少量的缩松缺陷,模拟和实际相吻合。     

Application of cast gamma TiAl for automobiles

Studies of cast gamma TiAl applied for engine valves and turbocharger confirmed excellent performances. The durability of TiAl valves was also proven. Two cast gamma TiAl alloys were developed for the engine valves and the turbine wheels of turbochargers. New precision casting process of LEVICAST and induction brazing process of the gamma TiAl and alloy steels were proposed as advanced processing technologies.     

TiAl基合金叶片吸铸成形缺陷的数值模拟

采用有限元软件ProCAST模拟TiAl基合金液在金属型真空吸铸成形铸造工艺中的充型凝固过程,分析在充型凝固过程中产生缺陷的原因,并进行了相关的实验验证。在模拟过程中发现铸件中确实存在模拟预测的缺陷,且缺陷主要集中在叶片隼部,在叶身部位出现少量的缩松缺陷,模拟和实际相吻合。