Synthesis of W-Y_2O_3 alloys by freeze-drying and subsequent low temperature sintering:Microstructure refinement and second phase particles regulation

In this work,W-Y2 O3 alloys are prepared by freeze-drying and subsequent low temperature sintering.The average size of reduced W-Y2 O3 composite powders prepared by freeze-drying method is only 18.1 nm.After low temperature sintering of these composite nanopowders,the formed W-Y2 O3 alloys possess a smaller grain size of 510 nm while maintaining a comparatively higher density of 97.8%.Besides a few submicron Y2 O3 particles(about 100-300 nm)with a W-Y-O phase diffusion layer on their surface distribute at W grain boundaries,lots of nano Y2 WO6 particles(<20 nm)exist in W matrix.Moreover,many Y6 WO12(<10 nm)particles exist within submicron Y2 O3 particles.The formation of these ternary phases indicates that some oxygen impurities in the W matrix can be adsorbed by ternary phases,resulting in the purification of W matrix and the strengthening of phase boundaries.The combined action of the above factors makes the hardness of the sintered W-Y2 O3 alloys in our work as high as 656.6±39.0 HV0.2.Our work indicates that freeze-drying and subsequent low temperature sintering is a promising method for preparing high performance W-Y2 O3 alloys.     

通过离子掺杂剂界面偏析来提高氧化物弥散强化合金的机械性能

氧化物弥散强化钨合金(ODS-W)因具有显著提升的抗辐照能力、高温强度以及抗蠕变性能而展现出巨大的高温应用潜力.然而,分散在合金中的氧化物第二相颗粒容易在钨晶界处团聚并长大(甚至到微米尺寸),这大大抑制了它们对钨合金的强化效果.目前,如何有效细化和分散钨晶界处的氧化物第二相颗粒一直是人们面临的巨大挑战.在本文中,我们通...     

高温热变形条件下Ni-Ti形状记忆合金的微结构演变

采用真空感应法炼制了不同氧、碳含量的NiTi和NiTiNb形状记忆合金 .分析研究了合金的微观组织、相结构以及高温热变形对合金微观组织的影响 ,重点研究和探讨了合金微观结构在高温热变形过程中的演变规律 .确定了合金组织中TiNi基体相、Nb相及在晶界形成的氧化物和碳化物的形变特点 .结果表明 ,合金中C、O含量决定其组织中碳化物和氧化物的形态和含量 ,高温热变形时 ,TiNi基体相和Nb相粒子均产生较大塑性变形 .当合金中氧和碳含量较高时 ,氧化物和碳化物在变形时碎裂 ,在组织中的分布比铸态更均匀 .在本文研究的氧、碳含量的范围内 ,氧化物和碳化物的存在对合金的力学性能 ,如拉伸强度、延伸率等影响不大 .     

Wear-resisting Oxide Films for 900℃

A study was conducted to develop low-friction, wear-resistant surfaces on high temperature alloys for the temperature range from 26℃ to 900℃. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological properties. Improvement is needed at low temperatures where the oxide film, previously formed at high temperature, spalls due to stresses induced by sliding. Experiments with Ti, W and Ta additions show a beneficial effect when added to Ni and Ni-base alloys. Low friction can be maintained down to 100℃ from 900℃. For unalloyed Ni friction and surface damage increases at 400℃ to 500℃. Two new alloys were perpared based on the beneficial results of binary alloys and ZrO2 diffusion in Ni.Low friction at temperature above 500℃ and reasonable values (0.32~0.42) at low temperature are obtained.     

不同因素对钼及钼合金塑脆性能影响的研究

钼及其合金具有很好的高温强度和抗腐蚀性等优异性能,广泛应用于众多高科技领域.综述了C、N、O杂质元素、掺杂元素和稀土氧化物、常规的K、Si、Al、Ca、Mg、Fe等元素以及织构等因素对钼及钼合金塑脆性能的影响,总结了提高钼合金塑性的基本方法和规律.同时指出钼及钼合金今后研究的重点是提高合金的横向塑性,以使其得到更广泛的应用.     

合金元素复合化对Ti_(2)AlNb合金高温抗氧化性能影响EI北大核心CSCD

Ti_(2)AlNb合金具有良好的工艺性能、综合力学性能和较低的密度等性能优势,是新型航空发动机的重要选材之一。为拓宽Ti_(2)AlNb合金的应用范围,需对传统Ti_(2)AlNb合金进行合金成分优化和工艺组织调控以进一步增强其高温抗氧化性能。本研究在传统Ti-Al-Nb三元合金体系基础上,综合设计Mo,Zr,W等合金复合化的方法提高Ti_(2)AlNb合金的抗氧化能力,通过对新型Ti_(2)AlNb合金在750℃和850℃的氧化增重行为分析、氧化层特征结构分析、表面氧化物种类和合金成分过渡分布分析等,发现Mo合金元素引起Ti_(2)AlNb合金在750℃上升至850℃时抗氧化性能的明显下降,Zr合金元素则始终保持着Ti_(2)AlNb合金良好的高温抗氧化能力;更为深入的截面试样SEM表征可将氧化层结构细分为氧化物层、富氧扩散层和组织演变层,Zr和W合金元素对850℃高温氧化过程中不同氧化层结构具有协同抑制作用,因此提出通过Zr和W合金元素复合的方法作为新型Ti_(2)AlNb合金抗氧化合金成分优化方向。     

Fe-Ni基合金设计中前过渡族元素对结构与性能的影响EI北大核心CSCD

铁镍(Fe-Ni)基合金具有优异的高温强度、良好的强韧匹配以及耐腐蚀、抗氧化等特性,在核能、航空、航天领域应用广泛。然而,随着现代工业的飞速发展,材料的服役环境愈发苛刻,传统Fe-Ni基合金无法满足未来重大工程的应用需求。添加合金化元素是优化Fe-Ni基合金使役性能的重要手段,已成为当下的研究热点之一。本文综述了前过渡族元素添加对Fe-Ni合金相结构及性能的影响。基于相图、相变的热力学基础理论,重点讨论前过渡族元素(RE,Ti,V,Cr,Zr,Nb,Mo,Hf,Ta,W等)添加对合金物相结构的影响,论述Fe-Ni基合金成分-结构-服役性能的关系,指出当前元素改性Fe-Ni基合金的研究工作偏向于多元合金协同作用于Fe-Ni基合金,缺乏添加单一元素的研究与相应的热、动力学的数据支撑。提出在明确单一元素添加对Fe-Ni基合金结构及性能作用规律的基础上,探索不同元素的作用机理,建立相应的热、动力学数据库,优化合金在氧化过程中的模拟与计算的解决方法。     

A unified constitutive model for quasi-static flow responses of pure Ta and Ta-W alloys

This study aims to develop a unified constitutive model describing the flow behaviors of pure Ta and Ta-W alloys over a wide range of strain rate and temperature. The model was based on the previously suggested model by Nemat-Nasser and Isaacs [3] and was further extended to capture the hardening effects caused by the changes in solute contents and concentrations, and grain size; while interstitial solutes (C, N, and O) increased the thermal stress, substitutional solute (W) increased both the thermal and athermal stresses. The results showed that the developed model can provide a reasonable prediction on the flow behaviors of pure Ta and Ta-W alloys (Ta-2.47W, Ta-5.2W, and Ta-9.8W) with different grain sizes of 0.3-45 μm over a strain rate range of 1-10⁻⁶ s⁻¹ and a temperature range of 77-900 K without any change in the material constants used.     

聚变装置钨涂层面对等离子体材料的性能

对铜基体上真空等离子体喷涂1 mm的钨涂层进行了分析研究,主要包括微观结构、热力学属性以及成分分析.结果显示,钨涂层气孔率仅为7.6%,室温热导率达到79.7 W/(m·K),W/Cu结构界面结合强度高达45 MPa,这些结果对钨作为聚变装置面对等离子体材料的应用是令人鼓舞的.涂层材料的出气性能也是面对等离子材料的一个重要指标,钨涂层出气气体种类主要是氢气和水蒸气.而且在300℃经过4 h高温烘烤后出气率大幅度降低,更长时间的烘烤则对出气率影响不是太明显.因此可以看出钨涂层作为聚变装置面对等离子体材料的应用是可行的.     

Weakening Mechanisms of Platelike σ Phase on Ni-base Superalloys

On the basis of an investigation on σ phase inNi-base cast superalloy K24 and the results aboutσ phase in other Ni-base superalloys,an embrittl-ing mechanism and a softening mechanism,bywhich platelike σ phase weakens the Ni-basesuperalloys,have been proposed.It is consideredthat the platelike morphology and the habit precipi-tation along{111}of σ phase are necessary condi-tions for both mechanisms.The embrittling mecha-nism is dominant at room temperature and highstrain rate,and the softening mechanism is domi-nant at high temperature and low strain rate.Ac-cording to the idea of the softening mechanism andthe analyses of σ phase and alloy compositions,it isconsidered that Nb,Mo and W in the alloys may beresistant to the detrimental effect of σ phase on thestress-rupture properties of the alloys.     

Influence of oxygen content on the microstructure and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn-xO alloys after aging treatment

The influence of oxygen (O) content on the microstructure and mechanical properties of cold rolled Ti-32.5Nb-6.8Zr-2.7Sn-xO (TNZS-xO; x?=?0, 0.3, 0.6; mass%) alloys after aging at temperature range from 350 to 600?°C for 24?h was investigated. Results showed that the cold rolled TNZS-xO alloys possess single β phase. During the aging process, O could not only effectively suppress the precipitation of ω phase but also retard the formation and decomposition of α phase. In addition, the corresponding temperatures of the maximal volume fraction of α phase precipitation and the (α+β)/β transus temperatures of the TNZS-xO alloys were all increased with the increasing of O content. For mechanical properties, it was found that the strength and Young's modulus of the TNZS-xO alloys increased owing to the ω phase and/or α phase precipitation and decreased owing to the α phase decomposition. However, the elongation showed the opposite change tendency with the above mentioned strength. The mechanical properties of TNZS-xO alloys can be controlled over a wide range by subjecting to aging treatment and/or changing their O content. When aged at or below 450?°C, the TNZS-xO alloys exhibit great potential to become a series of new candidates for biomedical applications since they possess high strength (870–1460?MPa), low Young's modulus (45.1–75.6?GPa), high strength-to-modulus ratio (0.018–0.02) and appropriate elongation (7.2%–14.9%), which are superior to those of Ti-6Al–4?V alloy and suitable for the use as bio-implant materials.     

形变强化对93W-4.9Ni-2.1Fe合金组织及性能的影响

为研究形变强化工艺对93W-4.9Ni-2.1Fe性能的影响,采用大变形量旋转锻造工艺制备了93W-4.9Ni-2.1Fe合金,并利用SEM与TEM技术分析了旋转锻造态93W-4.9Ni-2.1Fe合金显微组织的形态与尺寸.结果表明:钨合金材料经形变强化后,钨晶粒内部出现由高密度位错形成的胞状组织以及长条状形变晶粒,且粘结相内位错密度较高;旋锻态93W-4.9Ni-2.1Fe合金在具有高强度的同时,保持着一定的延性;旋锻态钨合金的力学性能与变形量及粘结相的分布有关.     

Metastable Beta Titanium Alloys for Orthopedic Applications

This article provides an overview of metastable β titanium alloys either being utilized or being considered for use in orthopedic applications. The effects of thermomechanical processing on the mechanical properties (e.g., elastic modulus, tensile, wear and high cycle fatigue performance) of Ti‐15Mo‐0.2O, Ti‐12Mo‐6Zr‐2Fe (TMZF), Ti‐29Nb‐13Ta‐4.6Zr and Ti‐35Nb‐7Zr‐5Ta are reviewed. The osteointegration behavior of Ti‐29Nb‐13Ta‐4.6Zr and Ti‐35Nb‐7Zr‐5Ta‐O alloys is also presented.     

Si及时效对Fe-Al-Si阻尼合金性能的影响

为了进一步提高Fe-Al二元阻尼合金的阻尼性能和力学性能,并认识在较高温度下长时间使用对其阻尼性能的影响,利用倒扭摆、拉伸、光学金相等方法测试了微量Si元素和不同时效时间对Fe-Al基合金阻尼性能、力学性能、微观组织的影响.结果表明,在Fe-Al合金中添加少量Si元素,合金的阻尼性能、力学性能优于Fe-Al合金,晶粒也得到明显细化.350℃长时间时效前后,实验合金的阻尼性能、力学性能、微观组织保持稳定.Fe-Al-Si阻尼合金具有更加全面的阻尼和力学性能,并可在350℃下长时间使用,应用范围更广阔.     

银基钎料在制造业中的研究进展

钎料的性能很大程度上决定了钎焊接头的质量和钎料的应用范畴.银基钎料作为一类非常重要的硬钎焊材料,其填缝能力优异,强度与黄铜、低碳钢接近,可钎焊除铝、镁合金等轻金属之外的所有金属材料.因此,银基钎料广泛应用于航空航天、超硬工具等制造领域,并且受到国内外钎焊界学者们的高度关注.然而,银基钎料的发展及应用过程中仍存在以下问题:第一,钎料中贵金属银含量偏高(一般高于45%),导致钎料使用成本高;第二,银基钎料挤压、轧制、拉拔等加工过程中不可避免地存在夹杂物,影响钎料的使用性能和连接质量;第三,有益金属或合金调控钎料及其连接性能的机制较为复杂,尚未完全研究清楚;第四,传统制备银基钎料的方法产能低下;第五,银基钎料在制造业领域的应用研究尚未见系统报道.国内外对于银基钎料钎焊性能及工程应用方面的研究主要集中于:(1)开发多种节银降银钎料,主要是有益元素调控银基钎料连接性能方面的研究;(2)改进钎料的传统加工方法,提出新的制造方法,如粉末电磁压制成形、钎焊过程中原位合成、快速凝固、镀覆扩散组合等;(3)研究杂质元素(C、Ca、S、Al、Fe、Bi、Pb、O、N 等)的影响;(4)银基钎料形态创新研究,如三明治复合钎料(中间为铜合金、两边为银钎料)、箔带钎料、镀锡银钎料等;(5)工程应用研究,银基钎料在航空航天、汽车制造、电力能源等工业领域起着不可替代的作用,但目前国内外仍缺乏系统阐述该方面研究的报道.因此,本文对近20年国内外有关银基钎料的研究报道进行了评述,重点讨论了合金元素对银基钎料性能的影响.首先对银基钎料研究现状进行详述,总结了Cu、Zn、Sn、Ga、In、Ni、Mn、Cd、Li、Ce、La、P、Si、Pr在银基钎料中的优缺点,归纳了杂质元素C、S、O、N、Ca、Al、Fe、Pb、Bi的恶化作用.其次对银基钎料在航空航天、汽车制造、电力能源、超硬工具、家用电器、眼镜行业等制造业中的应用研究进行详细介绍.最后提出银基钎料研究和应用中的不足,为银基钎料的深入系统研究及相关技术发展提供理论指导.     

贮氢合金V3TiNi0.56Crx的充放电性能和吸放氢性能研究

以V2O5、TiO2等原料,用自蔓延高温合成法制备了钒基贮氢合金V3TiNi0.56Crx(x=0.1、0.3),用EDXRF、XRD等方法分析了合金的组织成分,用LK98BⅡ微机电化学分析系统、PCT测试仪分别测试了合金的充放电性能和吸放氢性能.结果表明:随Cr含量的增加,合金放电容量和吸氢量均降低;气态放氢平台的宽度变窄、倾斜度增加;电化学放电平台电压和气态放氢平台压力均增加;循环稳定性提高.     

Mg-Gd-Y合金的研究进展

已有的研究表明,Mg-Gd-Y系合金具有很好的室温强度和耐热性能,可以进一步扩大镁合金的使用温度范围和应用领域,在航空航天、汽车及电子等工业领域具有巨大的潜在应用价值.介绍了Mg-Gd-Y系合金产生的背景及发展现状,分析总结了Mg-Gd-Y系合金的强化机制、组织结构、力学性能、各种合金元素及微量元素在合金中的作用,并对Mg-Gd-Y系合金今后的发展趋势进行了展望.     

Mechanical performance of extruded Ti–46Al–5Nb–1W titanium aluminide

Abstract

Titanium aluminide alloys offer considerable promise for use in high temperature applications, such as gas turbines. In this study an extruded Ti–46Al–5Nb–1W alloy has been examined, in terms of its tensile and creep behaviour. A reasonably fine and uniform microstructure was found in this bar product. This gave excellent properties, with tensile strengths up to ～950 MPa at room temperature, along with 1% elongation. These properties were accompanied by a very good creep behaviour, with low primary strains at the lower stresses and very low secondary creep rates. Comparison of the creep properties of this titanium aluminide alloy with other similar compositions and some typical nickel alloys shows that it is significantly superior to first generation titanium aluminides but also nickel alloys, such as IN718 and Udimet 720Li. However, the strain controlled fatigue performance of the titanium aluminide alloy was significantly poorer than these same wrought nickel alloys.     

Effects of high-temperature ageing on the creep-rupture properties of high-tungsten cobalt-base superalloys

The effects of high-temperature ageing on creep-rupture properties were studied using cobalt-base superalloys containing about 14–20 wt% tungsten (W) at 1089 K (816 °C) and 1 311 K (1038 °C) in air. A high-temperature ageing for 1080 ks at 1273 K after solution treatment caused grain-boundary and matrix precipitates of W solid solution and carbide phases in these alloys, and grain boundaries were serrated especially in the alloys with higher W content. The high-temperature ageing largely improved the rupture life in the alloys with higher W content, particularly under lower stresses at 1089 K, whereas it caused the creep ductility to decrease a little in the alloy containing 20% W. The high-temperature ageing also improved the rupture life without decreasing creep ductility in these alloys under higher stresses at 1311 K. Under the same ageing conditions of 1080 ks at 1273 K, the initiation of grain-boundary cracks was retarded in the solution-treated and aged specimens, as well as in the aged specimens with serrated grain boundaries, for the alloys with higher W content at both 1089 and 1311 K. A large amount of grain-boundary serration also occurred in the non-aged specimens of the alloys with higher W content during creep at 1311 K, and contributed to the strengthening of the alloys. The solution-treated and aged specimen had almost the same rupture strength as the aged specimens with serrated grain boundaries in these cobalt-base alloys. The rupture strength of the solution-treated and aged specimens largely increased with increasing W content under the lower stresses at 1089 K and under the higher stresses at 1311 K. A ductile grain-boundary fracture surface, which was composed of dimples and grain-boundary ledges associated with grain-boundary precipitates, was observed in the solution-treated and aged specimens, as well as in the aged specimens with serrated grain boundaries at both 1089 and 1311 K. The fracture surface of the non-aged specimens was a brittle grain-boundary facet at 1089 K, but it became a ductile grain-boundary fracture surface, as serrated grain boundaries were formed owing to grain-boundary precipitates occurring during creep at 1311 K.     

难熔高熵合金研究进展

高熵合金是近年来的新兴领域,与传统合金不同,其一般是由五种或者五种以上主要元素组成,每种主元的含量在5%~35%(原子分数)之间,多种元素混乱排列却拥有简单的相结构,高熵合金的优点显著,发展空间巨大。以难熔金属元素为基础的难熔高熵合金近年来大受关注,含有3种及以上的难熔金属组成的高熵合金称为难熔高熵合金,由于难熔金属的熔点均较高,因此难熔高熵合金表现出了较好的高温力学性能和高温抗氧化性能以及耐腐蚀性能,受到大众欢迎,有望取代传统的高温合金。详细的阐述了难熔高熵合金的制备方法、相结构、力学性能、抗氧化性能与耐腐蚀性能,最后对难熔高熵合金的发展进行了展望。