定向凝固TiAl合金成分−组织−性能研究进展

TiAl合金由于其低密度和高比强度,在航空材料中展现出良好的应用前景。通过定向凝固控制TiAl合金晶体取向,有助于大幅提升合金高温性能和服役温度,促进TiAl合金在新一代航空发动机上的应用。综述了近年来TiAl合金定向凝固的研究方法和成分?组织?性能关系的研究进展,总结了国内外定向凝固TiAl合金的主要研究单位及研究主题,简要介绍了定向凝固方法与模壳材料的应用情况。从合金成分角度,分析并总结了α、β相稳定元素和其他常见元素对定向凝固组织和性能的作用;从力学性能角度,介绍了定向凝固高Nb?TiAl合金在高温拉伸、蠕变、高周疲劳性能上的优势及相关机理;从定向凝固工艺角度,归纳了生长速率和温度梯度对合金凝固路径、片层取向及宏观、微观偏析的影响。展望了定向凝固TiAl合金的未来发展方向。     

Microstructure and Mechanical Properties of Two-phaseTiAl Alloys in Lamellar Form

In two-phase TiAl alloys, the lamellar structures are of special interest and importance since they are so common and persistent. not only under as-cast conditions but also after thermal treatment. However. the lamellar structures are still poor in ductility,although they are beneficial for toughness and high temperature strength. This article will review the recent progress made in understanding the basic mechanical properties of the γ and α2 phases which comprise the two-phase alloys in Iamellar form, and discuss how an improved balance of strength and ductillty in the lamellar form may be achieved     

NiAl（Fe）合金组织和拉伸性能的研究

采用光学显微镜、扫描电镜（ＳＥＭ）、透射电镜（ＴＥＭ）、电子探针（ＥＰＭＡ）、Ｘ射线（ＸＲＤ）和选区电子衍射分析（ＳＡＥＤ）研究了ＮｉＡｌ（Ｆｅ）合金的显微组织及拉伸性能。结果表明，铸态ＮｉＡｌ（Ｆｅ）合金经均匀化退火后的组织由β及β＋γ＇相组成。韧性相γ＇相能阻止裂纹扩展，有利于改善合金的室温塑性。比较发现，Ｎｉ５０Ａｌ２０Ｆｅ３０合金具有最佳的室温塑性，其拉伸断口由β相的解理断口和β＋γ＇相的     

熔模精密铸造TiAl基金属间化合物研究进展

TiA1基金属间化合物作为一种新型轻质高温结构材料,在航空航天和汽车等领域具有广阔的应用前景。熔模精密铸造是当前普遍采用的制备TiAl基金属间化合物的方法。主要介绍了熔模精密铸造TiA1基合金的铸件以及型壳用粘结剂及耐火材料的发展现状,TiA1合金的熔炼技术及最新研究进展,并对TiAl基金属间化合物熔模精密铸造技术的不足进行了分析并提出了展望。     

Diffusion Bonding of Dissimilar Intermetallic Alloys Based on Ti_2AlNb and TiAl

Direct diffusion bonding of an orthorhombic Ti 2 AlNb base alloy to a TiAl base alloy, Ti-22Al-23Nb-2Ta and Ti-46.2Al-2Cr-2Nb-0.15B (at. pct), was carried out and the interface microstructure, formation of new phase at the interface and joint strength were characterized. At low temperature, a new phase with AlNb 2-structure, Al(Nb, Ti) 2 , was formed in the interface region adjacent to the O base alloy. The α 2 was found to be the major reaction product and developed in the interface region adjacent to the ...     

Processing and Applications of Intermetallic γ‐TiAl‐Based Alloys

Development and processing of high‐temperature materials is the key to technological advancements in engineering areas where materials have to meet extreme requirements. Examples for such areas are the aerospace and spacecraft industry or the automotive industry. New structural materials have to be “stronger, stiffer, hotter, and lighter” to withstand the extremely demanding conditions in the next generation of aircraft engines, space vehicles, and automotive engines. Intermetallic γ‐TiAl‐based alloys show a great potential to fulfill these demands.     

High Temperature Mechanical Properties of Ni-Al-Cr Based Alloys for Advanced Die-Materials Applications

In this study, we report on advanced Ni3Al based high temperature structural alloys with Zr and B addition in order to apply in the fields of die-casting and high temperature press forming as die materials. Microstructures and mechanical properties of Ni3Al based intermetallic alloys produced by vacuum arc melting were investigated in terms of phase analysis by using a scanning electron microscope （SEM） equipped with an X-ray energy dispersive spectrometer （EDS）, an X-ray diffractometer （XRD） and tensile test. The duplex microstructural feature consisting of γ＇ matrix phase and small intermetallic dispersoids was observed to be distributed over the whole microstructure. The ultimate tensile strength of the present alloy was superior to commercial iron-based and Ni-based die-materials especially in the high temperature region.     

Production, Properties and Applications of Bulk Amorphous Alloys

A review is given of recent work concerned with the production method, the characteristic properties(1) Bulk amorphous system; (2) Mechanical and magnetic properties of bulkamorphous alloys; (3)application of bulk amorphous alloys.     

Microstructure and Magnetic Properties of NiP Alloys

Ni-P alloys were prepared by electrodeposition on a copper substrate at different plating conditions (applied potential and deposition time). The morphology, composition, microstructure, structure, and magnetic properties of the films were investigated by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, and vibrating sample magnetometry, respectively. The phosphorous content is about 8.6–12.2 at.%. The deposits exhibit either a nanocomposite structure where Ni(P)–1 and Ni(P)–2 solid solutions are embedded into an amorphous matrix, or a mixture of Ni₂P phosphide and Ni(P)–1 and Ni(P)–2 solid solutions. The coercivity and magnetization are plating condition dependent. All samples exhibit a soft magnetic character with coercivity lower than 58 Oe. The squareness ratio Mr/Ms values that are in the range 0.019–0.123 correspond to a multidomain (<0.1) for all samples except sample B (?1.15 V, 10 min) which falls into a pseudo-single domain (Mr/Ms = 0.123).