TiAl基合金熔模精密铸造技术的发展现状

TiAl基合金作为一种新型轻质高温结构材料,以其密度低、比强度和比模晕高,具有较好的抗氧化和蠕变性能以及优异的抗疲劳性能,在航空航天和汽车等领域具有广阔的应用前景.本文主要介绍了TiAl基合金的熔炼技术、熔模精密铸造技术及应用研究,并提出了TiAl基合金熔模精密铸造技术的不足与展望.     

Al液对TiAl合金表面渗氮层腐蚀机理研究

对TiAl基合金高温渗氮层的微观组织、显微硬度、腐蚀层进行了研究.结果表明:经高温渗氮处理后,渗氮层显微硬度明显提高,TiAl基合金的渗氮层结构由氮化物层与过渡层组成,通过对铝液腐蚀TiAl基合金渗氮处理试样表面微观结构分析,渗氮处理有利于提高TiAl基合金表面的耐蚀性能,并分析了腐蚀机理.     

γ—TiAl基合金的高温氧化性能及防护方法

γ－TiAl基合金密度低，并具有较高的高温强度，良好的抗氧化性能和抗蠕变能力，被认为是一种极具应用潜力的高温结构材料．但由于该合金的室温塑、韧性较差，限制了其在实际中的应用．对此，材料科学工作者进行了大量的研究，在不断加深对TiAl合金变形机理的了解基础上，采用合金化、不同的热处理工艺等手段，使得该合金的室温塑、韧性等均得到了一定的提高．然而，作为高温结构材料，对γ－TiAl基会金的高温性能的研究不容忽视．其中，高温氧化是TiAl合金高温下的一个重要失效模式，提高γ－TiAl合金高温氧化的极限温度也是提高该合金…     

机械合金化和微量添加剂对TiAl基合金显微组织及高温抗氧化性能的影响

研究了采用机械合金化方法制备TiAl基合金的工艺及其对显微组织的细化作用，概述了一系列添加剂对TiAl基合金高温抗氧化性能的影响。     

添加微量Sb对Mg—9Al—0.8Zn合金蠕变抗力及微观组织的影响

对Mg-9Al-0.8Zn－（0．1,0．4,0．7）Sb合金的高温蠕变性能及其微观组织进行了观察。结果表明,添加微量Sb可以显著提高Mg-9Al-0.8Zn（AZ91)合金在150－200℃区间的蠕变寿命,大幅度降低其稳态蠕变速率。使用扫描电镜和透射电镜观察分析了高温形变前后试样的显微组织及变化,在此基础上探讨了AZ91合金高温蠕变机制及添加Sb对其抗蠕变性能的改善机理。     

提高TiAl基合金室温塑性的方法

TiAl基合金具有密度低、高温性能好等优点，但室温塑性低一直是阻碍TiAl基合金应用的重要原因。本文总结了TiAl基合金的室温塑性的主要影响因素，以及通过添加合金化元素、改善加工工艺等方法来控制显微组织、提高TiAl基金合金的室温塑性的研究进展。     

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。     

含β相的TiAl基金属间化合物组织与性能的优化(英文)

从合金相的结构与相图入手,探讨了B2型TiAl基合金(以γ相为基、含β/B2相的TiAl合金)成分、结构、组织与性能的相关性,分析了β/B2相细化合金的组织和提高材料的高温变形能力的原因,并阐述了B2型TiAl基合金超塑性变形的机理。在TiAl基合金中添加适量的β稳定型元素,形成较稳定的B2结构的有序相,有利于细化晶粒和提高材料的高温变形能力。这种B2型TiAl基合金可通过掺杂微量低序数元素以及随后的热加工工艺提高其综合性能,包括变形能力和高温性能。     

间隙原子C在γ-TiAl基合金中的研究进展

铸造TiAl合金作为新型轻质高温结构材料其显微组织粗大,高温服役环境下强度和蠕变抗力不足成为限制其工业化应用的关键,而合金化则被认为是改善合金显微组织和力学性能的有效途径。综述间隙原子C在TiAl合金应用中的研究进展,重点介绍C在TiAl合金中的固溶极限及影响因素,简述TiAl合金中碳化物的结构、形态、分布及析出行为,并分析间隙原子C对合金显微组织及高温强度和蠕变抗力的影响及作用机理,对C在TiAl合金中的进一步研究应用提出建议。     

Ti3Al基合金的热处理显微组织与蠕变性能

对Ti_3Al基合金Ti_3Al-26M,Ti_3Al-11.5M和Ti_3Al-22M(wt%)(M=Nb,Mo,V)的热处理与显微组织和显微组织与蠕变性能之间的关系进行了探讨。结果表明:同一合金在不同热处理条件下的显微组织具有不同的特征和尺寸,而在同一热处理条件下的3种合金显微组织特征相同,只是晶粒的尺寸不同。高温蠕变性能测定表明,Ti_3Al-26M合金的蠕变性能优于Ti_3Al-11.5M和Ti_3Al-22M合金。Ti_3Al-26M合金经β固溶处理的魏氏组织的蠕变性能最好,经α_2+β固溶+时效和工厂处理的等轴组织蠕变性能次之。Ti_3Al-26M合金α_2+β固溶+时效状态的稳态蠕变速率与温度和应力的关系研究表明。随着温度和应力的增加稳态蠕变速率明显增加,并且随温度影响更为明显。     

Assessment of Titanium Aluminide Alloys for High-Temperature Nuclear Structural Applications

Titanium aluminide (TiAl) alloys exhibit high specific strength, low density, good oxidation, corrosion, and creep resistance at elevated temperatures, making them good candidate materials for aerospace and automotive applications. TiAl alloys also show excellent radiation resistance and low neutron activation, and they can be developed to have various microstructures, allowing different combinations of properties for various extreme environments. Hence, TiAl alloys may be used in advanced nuclear systems as high-temperature structural materials. Moreover, TiAl alloys are good materials to be used for fundamental studies on microstructural effects on irradiation behavior of advanced nuclear structural materials. This article reviews the microstructure, creep, radiation, and oxidation properties of TiAl alloys in comparison with other nuclear structural materials to assess the potential of TiAl alloys as candidate structural materials for future nuclear applications.     

锶和钙在镁-铝系合金中的应用及研究进展

论述了耐热镁合金的研究现状。介绍了碱土元素Ca和Sr对Mg-Al系合金的铸造性能、微观组织、拉伸性能和抗蠕变性能的影响。同时对Ca、Sr在镁合金中应用前景作了展望。     

α2-Ti-25Al-xNb合金力学性质的第一原理计算

采用第一原理赝势平面波方法计算了D0_19结构的α_2-Ti-25Al-xNb(x=O—12,原子分数,%)晶体的弹性模量(B, G和E)和抗拉强度(σ_b),并利用Cauchy压力(c_(12)-C_(44))与G/B比值表征和评判了不同浓度Nb合金化时α_2一Ti-25Al- xNb合金的韧脆化倾向.结果表明:在x=2—12时,α_2-Ti-25Al-xNb晶体的抗拉强度(σ_b)与σ_2相合金的弹性模量(B, E和G)随x增加而增大;在x=0—6时,α_2-Ti-25Al-xNb合金脆性有一定改善,且x值越大韧化效果越好;但在x=7—9时,相对于α_2-Ti_3Al,合金脆性不但没有得到弱化,反而随x增加而加剧;随后,当x进一步增大时,合金脆性又随x增加再次得到改善,至x=12时,α_2-Ti-25Al-xNb合金的韧化效果最好.通过电子态密度(DOS)和投影电子态密度(PDOS)等电子结构的分析,初步解释了Nb的这种强化与韧化作用.     

Multiphase intermetallic alloys for structural applications

Current more or less progressed developments on the base of intermetallic phases usually aim at new materials with the highest possible strength, creep resistance and oxidation resistance at the highest possible temperature and tolerable brittleness at lower temperatures for structural applications at high temperatures. Intermetallic alloys offer advantageous possibilities for reaching these aims by appropriate combination of phases and optimisation of phase distribution. This is exemplified with respect to strength and creep resistance by recent studies on NiAl alloys with strengthening Laves phase and multiphase TiAl alloys. The beneficial effects of additional softening phases on deformability and toughness are demonstrated by the results of recent studies on Laves phase alloys with disordered Fe–Al phase, NiAl alloys with disorderd Ni–Fe phase and partially transformed martensitic NiAl alloys. Mechanisms and problems are discussed and perspectives are outlined.     

Sb低合金化对Mg—9Al基合金显微组织和力学性能的影响

研究了合金元素Ｓｂ 对Ｍｇ９Ａｌ０ ．８Ｚｎ（ＡＺ９１） 基合金显微组织和力学性能的影响。结果表明,Ｓｂ加入后改善了合金的铸态组织, 使粗大的树枝晶变得更细小、弥散,Ｓｂ 主要是以弥散的第二相Ｍｇ３Ｓｂ２ 的形式分布于基体中。由于该相致密, 熔点高, 热稳定性好, 强化了晶界, 使得合金室温和高温力学性能得到一定的改善, 尤其使得抗高温蠕变性能大幅度提高, 塑性并没有受到明显损害。     

Deformation behaviour of intermetallic NiAl–Ta alloys with strengthening Laves phase for high-temperature applications IV. Effects of processing

The properties of the intermetallic NiAl–Ta–Cr alloy IP75 with strengthening Laves phase were studied as a function of alloy processing procedure: investment casting, hot extrusion of cast material, hot isostatic pressing (HIP), powder injection moulding (PIM) of pre-alloyed powder, and isothermal forging of HIPped material. Powder-metallurgically processed materials show finer microstructures and correspondingly reduced brittle-to-ductile transition temperatures (BDTT), lower yield stresses at all temperatures and lower creep resistances at high temperatures than cast materials. The lowest BDTT was obtained for isothermally forged material, whereas the highest yield stress was observed for remelted cast material. The effects of processing on the mechanical behaviour can be used for adjusting the property spectrum to specific applications. IP75, which is attractive for high-temperature applications because of high strength at temperatures above 1000 °C in combination with tolerable brittleness at room temperature as well as high corrosion and thermo-shock resistance, is the subject of an ongoing development aiming at applications in stationary gas turbines.     

Influence of microstructure and notch fabrication on impact bending properties of tungsten materials

Refractory materials, in particular tungsten base materials are considered as primary candidates for high heat load applications in future nuclear fusion power plants. Promising design outlines make use of the high heat conductivity and strength of W-1%La₂O₃ (WL10) as structural material. Here, the lower temperature range is restricted by the transition to a steel part and the upper operation temperature limit is defined by the onset of recrystallization and/or loss of strength, respectively. The most critical issue of tungsten materials in connection with structural applications, however, is the ductile-to-brittle transition. Another problem consists in the fact that especially refractory alloys show a strong correlation between microstructure and their manufacturing history. Since mechanical properties are defined by the underlying microstructure, refractory alloys can behave quite different, even if their chemical composition is the same. Therefore, the fracture behavior of several tungsten based alloys was characterized by standard Charpy tests which have been performed up to 1100 °C in vacuum. Due to their fabrication history (powder mixing, pressing, sintering, rolling or swaging) all materials had specific microstructures which often led to typical delamination fractures. The influence of the microstructure characteristics like grain size, anisotropy, texture, or chemical composition as well as the effect of notch machining was investigated. All results are discussed and assessed with respect to the optimization of future component fabrication for high temperature nuclear fusion applications.     

WC-Co-Re cemented carbides: Structure,properties and potential applications

Cemented carbides of the WC-Co-Re system represent a new class of hard materials having a significantly increased Young's modulus, hot hardness and high temperature creep resistance. The WC-Co-Re phase diagram was evaluated and compared with the corresponding WC-Co phase diagram. Physical and mechanical properties of such composites were measured at room and elevated temperatures and compared with those of conventional WC-Co cemented carbides. Microstructures of the WC-Co-Re cemented carbides at different carbon contents, binder contents and WC grain sizes were examined. Rhenium being dissolved in the Co-based binder is found to be a very strong grain growth inhibitor with respect to WC coarsening during liquid-phase sintering. The Young's modulus, hot hardness and high temperature creep resistance of the WC-Co-Re cemented carbides are greater than those of conventional WC-Co cemented carbides. Due to their unique properties the WC-Co-Re materials can find applications in use in high-pressure high-temperature components for synthesis of diamond and c-BN and cutting Ni-based super alloys and other heat-generating workpiece materials.     

玻璃工业用铂合金与复合材料

评述了各种铂材在玻璃工业中的应用和它们的主要特性。基于铂的高温化恘性能和力恘性能稳定性以及高的抗熔融玻璃浸润性,铂合金、铂复合材料和涂层材料成为制造高级玻璃和玻璃纤维的最佳高温结构材料。介绍和评述了玻璃工业用各种铂材,包括Pt、Pt固溶体合金(Pt-Rh、Pt-Rh-Au、Pt-Pd-Rh)、铂复合材料(颗粒弥散复合材料、层状复合材料和包覆复合材料)和先进铂涂层材料的特性和在玻璃工业中的具体应用。