机械合金化合成Fe-Ni-C系非晶态合金

用机械合金化方法合成了Fe—Ni—C系非晶态合金,用X射线衍射仪对球磨不同时间的Fe—Ni—C系混合粉末进行了分析．结果表明：在Fe—Ni合金中加入C可促使其形成非晶;原子分数分别为Fe40Ni40C20、Fe60Ni20C20的混合粉末在一定的机械合金化条件下可获得非晶．     

Fe基非晶合金粉末的研究进展

非晶合金粉末是指快冷雾化合金液滴所制得的合金粉末,其中Fe基非晶合金粉末因具有生产成本低廉和应用前景广阔等优势,一直备受青睐。同时,Fe基非晶合金粉末的应用也为块体Fe基非晶合金应用难的问题提供了一条崭新的途径。本文综述了Fe基非晶合金粉末的研究进展,对其在涂层制备、磁性材料、激光3D打印、废水处理4个方面的研究现状进行了归纳分类与总结,并分析了Fe基非晶合金粉末在各领域的应用优势。最后指出Fe基非晶合金粉末在制备高质量涂层、老化磁性粉末再利用及增材制造领域的研究方向,并展望了作为传感、控制等功能性器件的应用前景。此外,在薄膜等小尺寸、低维材料及柔性电子领域也展现出巨大的应用潜力。     

Ti811合金棒材的热稳定性能和蠕变性能

系统地研究了合金成分Ａｌ含量、拉应力和温度对Ｔｉ８１１合金棒材热稳定性能的影响，对合金的蠕变性能也进行了定性研究。结果表明：Ａｌ含量降低、应力和温度升高，则残余变形量增大；４２５℃／１００ｈ／４１０ＭＰａ热暴露，Ａｌ含量大于８（ｗｔ％）时，合金的热稳定性塑性急剧降低；不高于４７５℃暴露（０～４７５℃／１００ｈ／４１０ＭＰａ）以及４２５℃不同应力热暴露（０～４９０ＭＰａ／１００ｈ／４２５℃），合金具有较好的热稳定性。采用ＳＥＭ和ＴＥＭ技术分析了性能改变的原因。     

High-cycle fatigue behaviour and mechanism analysis of a forged TiZr-based alloy

Fatigue resistance, particularly the endurance limit, is an important design consideration in engineering applications for TiZr-based alloys. The investigated Ti–20Zr–6Al–4?V (wt-%) alloy exhibited a high fatigue endurance limit of 775?MPa. Results showed that severe local stress concentration due to extensive dislocation pile-up at α/β interfaces was responsible for the crack initiation. A transition from a tensile mode to a shear mode crack was observed during crack propagation. Many striations as well as some micro-cracks which can improve the resistance to crack propagation exist in the stable crack-propagation region. A localised deviation between the crack-growth direction was also found, and this outcome combined with micro-cracks and tear ridge may be attributed to varied crystallographic orientations between different phases.     

Cu-2.32Ni-0.57Si-0.05P合金热压缩变形研究

在Gleeble-1500D热模拟试验机上,对Cu-2.32Ni-0.57Si-0.05P合金在应变速率为0.01～5s-1、变形温度为600～800℃、最大变形程度为60%条件下,进行恒温压缩模拟实验研究.分析了实验合金在高温变形时的流变应力、应变速率及变形温度之间的关系,研究了变形温度对合金显微组织的影响.计算了合金高温热压缩变形时的应力指数n、应力参数α、结构因子A以及平均热变形激活能Q.结果表明:合金的流变应力随变形温度升高而降低,随应变速率提高而增大.热变形过程的流变应力可用双曲正弦本构关系来描述.当变形温度高于750℃时,合金流变曲线呈现出明显的动态再结晶特征,合金显微组织为完全的动态再结晶组织.合金的热加工宜在应变速率为0.1～1s-1、温度为700～800℃范围内进行.     

On the precipitation behaviour of 7055 aluminium alloy during high-speed cutting

ABSTRACT

The following paper examined changes in the microstructure of 7055 aluminium alloy before and after high-speed cutting (HSC) were examined, for various (T6, T7, and T84) heat treatment conditions. In the T6 state, the results demonstrated that the number of η^″ particles gradually reduced and there was pinning in the η^″ particles. After both the T7 and T84 heat treatments, a dislocation was observed in the microstructure by transmission electron microscopy. Grain boundaries in the T6 state were continuous with no obvious non-precipitate zone before HSC. The grain boundary width in the T7 state before HSC was double the T6 value. The grain boundary width for the T84 state alloy was similar to that in the T7 state, but less clearly defined.

This is part of a thematic issue on Small Scale Mechanics - EUROMAT.     

Thermal behaviour of ESP ash from municipal solid waste incinerators

Stricter environmental regulations demand safer treatment and disposal of incinerator fly ashes. So far no sound technology or a process is available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the municipal solid waste (MSW) incinerator residues. To explore the efficiency of thermal stabilisation and controlled vitrification, the thermal behaviour of electrostatic precipitator (ESP) ash was investigated under controlled conditions. The reaction stages are identified with the initial moisture removal, volatilisation, melting and slag formation. At the temperature higher than 1100 °C, the ESP ashes have a quicker weight loss, and the total weight loss reaches up to 52%, higher than the boiler ash. At 1400 °C a salt layer and a homogeneous glassy slag were formed. The effect of thermal treatment on the leaching characteristics of various elements in the ESP ash was evaluated with the availability-leaching test. The leaching values of the vitrified slag are significantly lowered than that of the original ash.     

Thermal fatigue behavior of squeeze cast, discontinuous alumina-silicate fiber-reinforced aluminum alloy (A356) composite

Microstructural damage mechanisms owing to thermal cycling and isothermal exposure at elevated temperature are studied for a short alumina-silicate fiber-reinforced aluminum alloy (A356) composite produced by pressure casting. The tensile strength of the metal matrix composite is found to degrade considerably in each case. An X-ray double-crystal diffraction method is employed to study the mechanisms of recovery in the matrix. The fractal dimension of the X-ray “rocking curves” for individual grains in the composite reflects the substructure formation owing to the rearrangement of dislocations into subdomain walls. Recovery by polygonization is more pronounced in the case of thermal cycling than for equivalent isothermal exposure. The residual stresses in the matrix that provide the fiber clamping force undergo more relaxation in the case of isothermal exposure. The two competing damage mechanisms, thermally activated recovery by polygonization and relaxation of clamping stresses in the matrix, result in identical strength degradation (25%) for both thermal cycling and isothermal exposure.     

Thermoelectric behaviour of amorphous magnetic alloys

The Thermoelectric emfs of thermocouples formed by amorphous METGLAS 2826 (Fe₄₀Ni₄₀P₁₄B₆) and METGLAS 2826B (Fe₂₉Ni₄₉P₁₄B₆Si₂) with standard thermocouple wires like copper, chromel, alumel, etc., were measured as a function of temperature between −196° C and 30° C to assess their suitability as thermoelectric temperature sensors. Thermoelectric emfs generated by METGLAS 2826/Cu and METGLAS 2826B/Cu thermocouples at −196° C are about an order of magnitude smaller when compared to thermal emfs of a standard copper/constantan thermocouple at the same temperature.     

Biodegradable behaviour and fatigue life of ZEK100 magnesium alloy in simulated physiological environment

The fatigue life of ZEK100 magnesium alloy in the phosphate buffered solution for various immersion intervals was investigated by experiments and theoretical predictions. The biodegradable behaviours of ZEK100 magnesium alloy were also studied. Microstructure observation showed that the corrosion behaviours were characterized by pitting corrosion. The corrosion rate decreased a lot in the initial 7 d and then almost stayed unchanged. After 28 d immersion, the elastic modulus almost kept stable, while the yield strength and the ultimate strength decreased a lot, which indicated that corrosion had important effects on the tensile mechanical properties. It showed that the fatigue life of the samples under the same stress conditions decreased with increasing immersion time under the asymmetric stress‐controlled cyclic loading. Considering the effect of corrosion on the material failure, a modified fatigue life model was proposed for magnesium alloy under corrosion.     

Dynamic compressive behaviour and microstructural evolution of extrusion-shear deformed ZC61 alloy

In this study, a novel extrusion-shear (ES) deformation method was developed to prepare ZC61 alloy. The dynamic mechanical properties and microstructure of specimen were studied at a temperature in the range of 25–350°C and strain rate of 1300?s^?1. The results demonstrated by ES exhibited a strong {0001} basal texture, resulting in the obvious anisotropy. The shapes of stress–strain curves of samples exhibited significant differences at low temperature (<250 °C) when compression was carried out along extrusion direction (ED) and extrusion radial direction (ERD). Dynamic recrystallization occurred at the loading temperature of 300°C along ED due to the energy provided by high-density dislocation in twins. However, no obvious dynamic recrystallization was observed for the ERD samples.     

化学镀Ni-Co-P合金的晶化行为研究

为了改善镀液性能,扩大Ni-Co-P合金的应用范围,以硼酸为缓冲剂,柠檬酸钠为配位体化学镀Ni-Co-P合金,用扫描电镜(SEM)、差示扫描量热(DSC)和X射线衍射(XRD)等技术研究了Ni-Co-P合金镀层表面的微观形貌和晶化行为.结果表明,Ni-Co-P合金镀层在镀态时呈多晶态结构,有立方Ni-Co合金相和非晶相(以非晶相为主),镀层于339.4℃时转化为Ni3P相,其晶化行为与氨性缓冲介质中得到的Ni-Co-P合金有明显差异.Ni-Co-P合金在镀态时其表面有许多直径为1.9～4.8μm的圆形小颗粒;500℃处理后的镀层表面有一些直径为6～7μm的圆形大颗粒,表面呈胞状结构,每一胞状物由许多50～100nm的颗粒形成.本研究为Ni-Co-P合金应用提供了参考.