新型高温合金C－286热处理工艺研究

本文介绍了一种新型的铁基高温合金，并探讨了该合金的固溶及时效工艺对组织和性能的影响。     

含铌高温材料的研究进展

含铌高温材料是航空航天材料中极其重要的组成部分,在飞机发动机、涡轮盘、燃气轮机、核工业高温结构件等部位都有极其广泛的应用。针对三类含铌高温材料：镍基高温合金。铌基合金和γ-TiAl合金,介绍了目前国内外产品研究发展的最新情况。     

MIM Fe基合金的固溶强化

研究金属粉末注射成形(MIM)铁基合金在强还原性氢气氛烧结条件下的合金化强化效果。结果表明,添加Cu、Ni、Mo等元素能取得显著的固溶强化效果,其中成分为Fe-2Ni-2Cu-0.45Mo的机械性能达到σ_b=483 MPa,σ_s=340 MPa,δ=9％和HRB=83。     

Nb在变形高温合金中的作用

以载入《中国高温合金手册(2012年版)》的经过国家验收、鉴定或批量生产的变形高温合金为主要研究对象,通过大量的文献调研,总结了Nb在变形高温合金中的作用。总结表明,在高温合金中,Nb既是主要的固溶强化元素,又是主要的沉淀强化元素。在固溶强化型高温合金中,Nb主要形成NbC、Z-(Ni_0.04Cr_0.83Fe_0.13)_1.9(W_0.15Mo_0.09 Nb_0.76)_3.3 N等相,显著提高合金的蠕变强度,降低蠕变速率,同时能保证合金良好的焊接工艺性能;在沉淀强化型高温合金中,主要形成γ′-Ni₃(Al,Ti)相、γ″-Ni₃ Nb相、δ-Ni₃ Nb相、ε-Ni₃(Nb,Ti)相、Laves-(Fe Co Ni)_1.84(NbTiSi)相等,通过控制析出相尺寸、形貌和分布的变化来获得良好的综合性能。目前有接...     

铌合金抗高温氧化涂层研究现状及发展趋势

铌合金表面抗高温氧化防护涂层分为耐热合金涂层、贵金属涂层、铝化物涂层以及硅化物涂层等几类。本文综述了各类涂层材料的特点、应用、研发现状以及硅化物涂层的制备技术,对硅化物涂层研究中存在的问题及今后的发展方向进行了分析和探讨。     

粉末高温合金Udimet720Li γ′强化相析出行为

采用气淬炉模拟了粉末高温合金Udimet720Li经空冷、风冷及油冷等不同冷却路径的固溶处理过程,测试了经过两级时效处理的合金在650 ℃的拉伸性能,研究了拉伸变形后的位错组态,分析了冷却速率对γ′强化相析出规律及力学性能的影响。结果表明:粉末高温合金Udimet720Li的析出相强化机制为位错切过机制,二次γ′相尺寸越小,合金强度越高。合金二次γ′相的形核析出温度区间为900～1000 ℃,其尺寸与合金在该温度范围内的冷却速率成反比,冷却速率越大,γ′相尺寸越小,当冷速高于100 ℃/min时,合金强度达到应用要求。推荐粉末Udimet720Li合金盘件固溶处理的冷却方式为:在1000 ℃以上保持低冷却速率来降低淬火应力,然后选择油浴作为盘件淬火的冷却方式,入油温度应在1000 ℃左右。     

Mo-Nb合金单晶的高温力学性能

研究了晶向为111Mo-Nb合金单晶的高温力学性能。实验结果表明,随着少量溶质原子Nb的加入,Mo-Nb合金单晶的高温强度获得了明显的提高。在1873K和Nb含量在0～6%范围内时(文中合金元素Nb含量均为质量百分比,下同),Nb含量每增大1%,材料的高温屈服强度就增加约16～25MPa,当Nb含量在0～3%范围内时,随着Nb含量的增加,塑性急剧下降,而在3%～6%范围内时其下降幅度趋于平缓;同时,随着Nb浓度的增大,更多的Nb溶质原子增大了原子间扩散阻力,使材料高温稳态蠕变率减小,大大提高了材料的高温抗蠕变性能;在1773K/10MPa时Mo-Nb合金单晶的稳态蠕变率较纯Mo单晶的降低了3～4个数量级,分析认为其蠕变机制为扩散蠕变。     

GH708合金800℃拉伸塑性不合原因分析

GH708合金是某发动机用镍基高温合金。该合金W、Mo含量高达12％，Al、Ti含量达到3．5％，属典型的固溶强化 时效强化的难变形高温合金，在高温下固溶强化作用非常明显。     

Nb-Based Nb-Al-Fe Alloys: Solidification Behavior and High-Temperature Phase Equilibria

High-melting Nb-based alloys hold significant promise for the development of novel high-temperature materials for structural applications. In order to understand the effect of alloying elements Al and Fe, the Nb-rich part of the ternary Nb-Al-Fe system was investigated. A series of Nb-rich ternary alloys were synthesized from high-purity Nb, Al, and Fe metals by arc melting. Solidification paths were identified and the liquidus surface of the Nb corner of the ternary system was established by analysis of the as-melted microstructures and thermal analysis. Complementary analysis of heat-treated samples yielded isothermal sections at 1723 K and 1873 K (1450 °C and 1600 °C).     

合金元素对Cu—P合金高温性能的影响

用Gleeble1500高温拉伸试验机研究了添加元素Ag，Sb，Sn对Cu－P合金高温性能的影响．研究结果表明，Ag能显著提高Cu－P合金在室温下的综合性能，Sb和Sn能显著提高Cu－P合金在150～280℃时的强度，其中的Sn强化效果最好．但当合Sn＞5％时，会使Cu—6．5P合金的室温脆性增大．     

高温电连接器用导电弹性合金的研究

为满足承受175～200℃高溫电连接器的需要,作者研制出了一种Ni含量小于5％,并加入少量Al,Si,Cr,Mg等元素的高强度高导电铜合金(CE-4合金)。试验了时效温度,时效时间及变形度对该合金机械性能的影响,测定了室温电阻率和弹性模量以及它们与温度的关系,并测试了几种温度下的应力松弛性能。结果表明,在36％～50％变形度下,430～450℃时效1小时,合金具有最高的强度,σ_b:940～1000N/mm~2,σ_(0.2):800～850N/mm~2,良好的延性(δ:～5％),有与铍青铜相当的高的弹性模量(E:139000～140000N/mm~2)和高的导电性(20～23％IACS),以及优于铍青铜的抗应力松弛能力。将该材料加工装配成Y11型高温电连接器,经200℃,1000小时的例行试验,各项指标均能满足军用标准的要求。     

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Effect of tantalum (Ta) on strengthening and the relevant mechanism of Fe-C-Ta alloy were preliminarily studied by mechanical property testing and OM, SEM, TEM observation. The results show that the strength of the alloy can be improved greatly as the Ta content is increased from 0. 027% to 0. 059% while the impact energy is reduced 87J. However, the alloy with higher Ta content (0. 059%) still behaves better toughness. It was analyzed that both solution strengthening and precipitation strengthening are the main strengthening effects of Ta on the alloy. Both strength and plasticity of the alloy with higher Ta content (0. 059%) reach the optimum values after aging at 600?? for 1h due to the precipitations of the Ta contained carbides.     

Diffusion in High-Temperature Ferrochrome Alloy Oxidation

Simulation has been applied to the diffusion characteristics such as the effective component diffusion coefficients in Fe 35 mass% Cr (0.5-3.0) mass% Al bearing surface oxides at the time of peeling. The simulation results are in agreement with experimental data on the layerwise phase compositions of the oxides. The model is described for the diffusion in a three-layer oxide region. The research elucidates the formation mechanism for multilayer oxides, and also gives estimates of their effects on heat resistance.     

Study of Aging-Induced Degradation of Fracture Resistance of Alloy 617 Toward High-Temperature Applications

For the Alloy 617, the effect of aging on the fracture energy degradation has been investigated after aging for different time periods at 1023 K (750 °C). A sharp reduction in impact energy (by ~55 pct vis-à-vis the as-received material) after 1000 hours of aging, as evaluated from room-temperature Charpy impact tests, has been observed. Further aging up to 10,000 hours has led to a degradation of fracture energy up to ~78 pct. Fractographic examinations using scanning electron microscopy (SEM) have revealed a change in fracture mode from fibrous-ductile for the un-aged material to intergranular mode for the aged one. The extent of intergranular fracture increases with the increasing aging time, indicating a tendency of the material to undergo grain boundary embrittlement over long-term aging. Analysis of the transmission electron microscopy (TEM) micrographs along with selected area diffraction (SAD) patterns for the samples aged at 10,000 hours revealed finely dispersed γ′ precipitates of size 30 to 40 nm, rich in Al and Ti, along with extensive precipitation of M₂₃C₆ at the grain boundaries. In addition, the presence of Ni₃Si of size in the range of 110 to 120 nm also has been noticed. The extensive precipitation of M₂₃C₆ at the grain boundaries have been considered as a major reason for aging-induced embrittlement of this material.     

Study on the Strengthening Mechanism of Two-Stage Double-Peaks Aging in 7075 Aluminum Alloy

The mechanical properties and microstructure of 7075 aluminum alloy during the two-stage aging process have been studied by means of Rockwell hardness test, tensile test, X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM) and high-resolution TEM. The results illustrated that there existed double peaks for both the hardness and strength in 7075 aluminum alloy during the two-stage aging process. Furthermore, the aging time to reach the second peak was obviously shortened compared to single-stage aging process. At the first peak aging state, the strengthening effect of the alloy was dominated by high-density GP zones, but η′ phase (MgZn2) was mainly the strengthening phase at the second peak aging state.     

Inconel690合金高温高速热变形行为研究

在Gleeble-3800热模拟试验机上,采用热压缩实验研究了不同变形条件下Inconel 690合金的高温变形行为与组织演变特点.实验中采用的变形温度为1000～1200℃,变形量为70％,变形速率为1.0 ～80.0 s-1.根据实验结果获得了该合金的应力-应变关系,并对峰值应力进行了线性回归,由此得到了该合金的高温材料常数,激活能Q =417.6 kJ.mo1-1,α =0.003196 MPa-1,n=7.51,并最终得到了Incone1690合金的高温变形本构方程.通过金相显微镜研究了合金动态再结晶规律与温度和应变速率的关系,结果表明:变形温度对Inconel 690合金组织的影响很大,随温度的升高,动态再结晶百分数逐渐增加,且伴随着晶粒的长大;而提高应变速率,变形的时间缩短,位错密度迅速增大,动态再结晶的驱动力增加,也可以使再结晶后的晶粒细化;当温度为1150℃左右,应变速率50～80 s-1时,能够得到均匀细晶组织.     

TZM合金的组织及强化机理分析

采用粉末冶金法制备TZM合金,通过SEM和EDS检测手段观察其显微组织,并在此基础上分析TZM合金的三种强化,即固溶强化、第二相强化和形变强化的强化机理.