激光熔敷Mo2Ni3Si／NiSi金属硅化物耐磨复合材料涂层组织与抗磨性能

以Ni-42Mo-28Si和Ni-36Mo-24Si(质量分数计)合金粉末为原料，利用激光熔敷技术在1Crl8Ni9Ti不锈钢基材表面制得由三元金属硅化物Mo2Ni3Si初生树枝晶和枝晶间Mo2Ni3Si／NiSi共晶组织组成的复合材料涂层，考察了涂层镍含量及Mo2Ni3Si初生相体积分数对涂层在滑动干摩擦下的耐磨性的影响．结果表明：激光熔敷Mo2Ni3Si／NiSi金属硅化物复合材料涂层在滑动干摩擦条件下具有优异的抗磨性能；随着涂层中三元金属硅化物Mo2Ni3Si初生相体积分数的增加，涂层的耐磨性提高，摩擦系数降低；激光熔敷Mo2Ni3Si／NiSi金属硅化物复合材料涂层具有良好的载荷特性．     

激光熔敷Cr3Si／Cr2Ni3Si金属硅化物涂层耐磨性与耐蚀性研究

以 Cr- Si- Ni预合金化粉末为原料 ,采用激光熔敷技术在 1Cr18Ni9Ti不锈钢表面制备出以金属硅化物 Cr3Si为增强相、以复杂多元金属硅化物 Cr2 Ni3Si为基体的快速凝固金属硅化物冶金涂层 ,在滑动磨损条件下评价了其耐磨性能 ,并采用阳极极化方法分别评价了该涂层在 0 .5 mol/L 的 H2 SO4 及 3.5 % Na Cl溶液中的电化学耐蚀性能 .结果表明 ,在滑动磨损条件下 ,所研制的涂层具有优异的耐磨性能 ,在 0 .5 mol/L的 H2 SO4 及 3.5 % Na Cl水溶液中具有优良的电化学耐蚀性能 ,这归因于其组成相 Cr3Si及 Cr2 Ni3Si的优异耐磨耐蚀性 ,以及非平衡快速凝固过程导致的组织细化、致密化和均匀化 .     

激光熔覆Cuss/Cr5Si3金属硅化物复合涂层组织及耐磨性的研究

利用激光熔覆技术在奥氏体1Cr18Ni9Ti不锈钢表面制备出由Cuss增韧铜基固溶体(Cr5Si3)金属硅化物新型耐磨复合涂层,分析了其显微组织,并在室温干滑动摩损条件下评价其耐磨性能.结果表明:涂层中高硬度耐磨相Cr5Si3得到Cuss基体的有力支撑,同时由于Cuss的高导热、低摩擦及自润滑效果,使得复合涂层在室温干滑动磨损条件下具有优异的耐磨性能;随着铜基固溶体体积分数增加,涂层的硬度和耐磨性明显降低.     

Mg-3Al-0.4Si镁合金的高温磨损行为研究

在20~200℃温度下,利用销盘式磨损试验机研究Mg-3Al-0.4Si合金的磨损行为,评价载荷和温度对磨损速率的影响.应用扫描电子显微镜观察磨损表面形貌以确定高温下的磨损机制,通过光学显微镜观察磨损亚表层组织演变,然后采用显微硬度计测量硬度变化.研究结果表明:随着磨损温度提高,Mg-3Al-0.4Si合金的磨损率随载荷增加而上升的趋势更为明显.其磨损行为可分为轻微和严重磨损,增加磨损温度显著降低轻微-严重磨损转变载荷.轻微-严重磨损前后的亚表层组织和硬度变化表明,摩擦热诱发磨损亚表层发生动态再结晶(DRX)组织转变引起的热软化是造成轻微-严重磨损转变的主要原因.     

MoSi_2高温磨损行为的配副特性研究

在XP-5型高温摩擦磨损试验机上考察了MoSi2与Al2O3、SiC和Si3N4配对副在1000℃大气环境不同滑动速率下的摩擦磨损行为,利用扫描电子显微镜和X射线衍射仪分析了试样的磨损表面形貌和相组成.结果表明:随着滑动速率的增加,摩擦系数和MoSi2的磨损率均呈下降趋势,SiC为更适合于MoSi2的高温配对副材料.与Al2O3配对时,MoSi2的磨损机理主要表现为黏着和氧化;与SiC和Si3N4配对时,MoSi2的磨损机理为研磨、轻微氧化和点蚀.     

磨盘材料和温度对TC11合金磨损行为的影响

对TC11合金与两种不同硬度的GCr15和W6Mo5Cr4V2在25、400和600℃对摩时的磨损行为进行了研究.利用SEM、EDS以及XRD等对试样磨面和剖面的形貌、成分及结构进行了观察与分析.结果表明:TC11合金与三种不同硬度的磨盘对摩后,在25℃,磨损率均随载荷的增加而增加,且磨损率较高,磨损表面呈现黏着和犁沟特征,磨损机理为黏着磨损与磨粒磨损;在400℃,合金与低硬度GCr15对摩时,磨损表面被黑色光滑氧化物所覆盖,磨损机理为氧化轻微磨损;与高硬度GCr15对摩时,在50和150 N,磨损表面呈现黑色光滑氧化物和犁沟特征,磨损机理为氧化轻微磨损和磨粒磨损;在250 N,磨损机理为黏着磨损与磨粒磨损;与W6Mo5Cr4V2对摩时,磨损表面呈现犁沟特征,磨损机理为磨粒磨损;在600℃,TC11合金的磨损率均较低,且与两种不同硬度GCr15对摩后的磨损率均低于与W6Mo5Cr4V2对摩的磨损率,磨损机理均为氧化轻微磨损.在25和600℃,磨盘材料对合金的磨损率具有不同的影响,但不影响合金的磨损机理;在400℃,磨盘材料既影响磨损率也影响磨损机理.     

Al元素对Ni基合金摩擦学性能的研究

利用高能球磨和真空热压烧结技术制备了Ni Cr Mo和Ni Cr Mo Al两种不同的合金.研究了Al元素对合金的微观组织结构和机械性能的影响,考察了不同温度(RT~900℃)条件下合金的摩擦磨损性能,并对磨损机理进行分析.结果表明:Al元素的加入减少了合金粉末的团聚,促进了烧结过程中合金晶粒的长大,提高了合金的致密度和硬度;尤其在高温摩擦环境中,与Ni Cr Mo合金相比,含有Al元素的Ni Cr Mo Al合金能在摩擦表面形成由Mo O3、Ni O和Ni Mo O4等组成的摩擦层,且没有Cr2O3硬质相的生成,极大提高了其高温下的摩擦学性能.     

水润滑下等离子喷涂Cr_3C_2-NiCr涂层/增韧SiC陶瓷摩擦副的摩擦学特性

采用 MM- 2 0 0型摩擦磨损试验机考察了等离子喷涂 Cr3C2 - Ni Cr涂层 /增韧 Si C陶瓷摩擦副在蒸馏水润滑下的摩擦学特性 ,通过对磨损表面形貌和磨屑的电子探针和傅立叶转换红外光谱分析 ,探讨了其磨损机理 .结果表明 :在较低载荷下 ,Si C与水发生摩擦化学反应 ,在磨痕表面生成由 Si O2 和硅胶组成的表面膜 ,从而使得摩擦副呈现出优异的摩擦学特性 ;在较高载荷下 ,Si C陶瓷发生晶粒微观断裂 ,从而使得摩擦系数升高并出现较大波动 ,此时 Cr3C2 - Ni Cr涂层的磨损率显著增大 .     

TiAl合金表面热障涂层的组织结构及其高温磨损性能研究

利用EB-PVD技术在TiA l合金表面制备了扩散铝/YSZ热障涂层.采用SEM、EDS和XRD分析了涂层的微观组织及其相组成,并测试了显微硬度和耐磨性.结果表明：涂层表面YSZ层为致密柱状晶结构,由非平衡四方相t＇-ZrO2组成;涂层结构由表及里依次为YSZ/A l2O3/TiA l3/TiA l2/TiA l;涂层的显微硬度和高温磨损性能显著提高,其高温磨损机理为轻微的犁削和严重的粘附转移,体积磨损率约为TiA l合金磨损率的1/10.     

触变成型AZ91D镁合金的干滑动磨损机制图研究

磨损机制图是表征材料在特定接触模式、滑动速度、试验载荷下的磨损机制转换关系.本文作者以触变成形AZ91D镁合金为研究对象,试验在ASTM1045钢块上进行,在98~490 N的载荷及0.083~1.084 m/s的滑动速度范围内进行磨损率的测量,通过扫描电镜(SEM)、电子探针分析仪(EPMA)和X射线衍射仪(XRD)对磨损表面(断面)和磨屑的形态及微观结构进行观察,探讨了触变成型AZ91D镁合金在干滑动条件下的磨损机理并绘制了合金的磨损机制图.结果表明:触变成形AZ91D镁合金在干滑动条件下的磨损行为可分轻微磨损和严重磨损,前者在稳定情况下进行,接触面温度存在热平衡效应,其磨损量与滑动距离成线性增加,而严重磨损的磨损量随滑动距离剧烈增加.轻微磨损又包括以氧化与磨粒的混合磨损和剥层磨损两种机制,其磨损的转变逐渐发生,磨损率无明显差异;严重磨损主要以严重塑性变形引起的磨损和熔融磨损进行,其转变会导致磨损率的剧烈增加.磨损试验中,接触面温度与表达式(F~(1/4)V~(1/2))存在函数关系,除熔融磨损外,轻微磨损到严重磨损的转变发生在摩擦面温度75℃±5℃左右.     

The 7th International Conference on Fluid Mechanics May 24-27,2015,Qingdao,China

正http://www.icfm7.org First Announcement and Call for PapersThe objective of International Conference on Fluid Mechanics(ICFM)is to provide a forum for researchers to exchange new ideas and recent advances in the fields of theoretical,experimental,computational Fluid Mechanics as well as interdisciplinary subjects.It was successfully convened by the Chinese Society of Theoretical and Applied Mechanics(CSTAM)in Beijing(1987,     

INFORMATION FOR CONTRIBUTORS

Contributions： The Journal, Acta Mechanica Solida Sinica, is pleased to receive papers from engineers and scientists working in various aspects of solid mechanics. All contributions are subject to critical review prior to acceptance and publication.     

Preface

This special issue of PARTICUOLOGY is devoted to the first UK-China Particle Technology Forum taking place in Leeds, UK, on 1-3 April 2007. The forum was initiated by a number of UK and Chinese leading academics and organised by the University of Leeds in collaboration with Chinese Society of Particuology, Particle Technology Subject Group （PTSG） of the Institution of Chemical Engineers （IChemE）, Particle Characterisation Interest Group （PCIG） of the Royal Society of Chemistry （RSC） and International Fine Particle Research Institute （IFPRI）. The forum was supported financially by the Engineering and Physics Sciences Research Council （EPSRC） of United Kingdom,     

基于鲁棒滤波的捷联导引头视线角速度估计方法

针对捷联导引头无法直接获取视线角速度等信息的问题,研究了鲁棒滤波在大气层外飞行器捷联导引头视线角速度估计中的应用。为了建立非线性滤波估计模型,考虑目标视线角速度的慢变特性,采用一阶马尔科夫模型建立了状态方程;推导了视线角速度的解耦模型,并建立了量测方程;考虑到实际应用中存在系统噪声统计特性失准的问题,基于Huber-Based鲁棒滤波方法,设计了视线角速度滤波器,并完成了基于Huber-Based滤波方法和扩展卡尔曼滤波方法的数学仿真。仿真结果表明Huber-Based滤波方法的视线角、视线角速度及视线角加速度估计精度分别达到0.1140'、0.1423'/s、0.0203'/s2,而扩展卡尔曼滤波方法的视线角、视线角速度及视线角加速度估计精度仅分别为0.6577'、0.6415'/s、0.0979'/s~2。仿真结果证明了该方法可以有效地估计出相对视线角速度等信息,并且在非高斯噪声的条件下,依然可获得较高的估计精度,具有一定的鲁棒性。     

Guide for authors

正Each of the sections below provides essential information for authors.We recommend that you take the time to read them before submitting a contribution to Acta Mechanica Sinica.We hope our guide to authors may help you navigate to the appropriate section.How to prepare a submission This document provides an outline of the editorial process involved in publishing a scientific paper in Acta Mechanica     

Use specification of multiscale materials for life spanned over macro-, micro-, nano-, and pico-scale

Multiscale material intends to enhance the strength and life of mechanical systems by matching the transmitted spatiotemporal energy distribution to the constituents at the different scale, say—macro, micro, nano, and pico,—, depending on the needs. Lower scale entities are, particularly, critical to small size systems. Large structures are less sensitive to microscopic effects. Scale shifting laws will be developed for relating test data from nano-, micro-, and macro-specimens. The benefit of reinforcement at the lower scale constituents needs to be justified at the macroscopic scale. Filling the void and space in regions of high energy density is considered.Material inhomogeneity interacts with specimen size. Their combined effect is non-equilibrium. Energy exchange between the environment and specimen becomes increasingly more significant as the specimen size is reduced. Perturbation of the operational conditions can further aggravate the situation. Scale transitional functions and/or f_j/j+1 are introduced to quantify these characteristics. They are represented, respectively, by , and (f_mi/ma,f_na/mi,f_pi/na). The abbreviations pi, na, mi, and ma refer to pico, nano, micro and macro.Local damage is assumed to initiate at a small scale, grows to a larger scale, and terminate at an even larger scale. The mechanism of energy absorption and dissipation will be introduced to develop a consistent book keeping system. Compaction of mass density for constituents of size 10⁻¹², 10⁻⁹, 10⁻⁶, 10⁻³ m, will be considered. Energy dissipation at all scales must be accounted for. Dissipations at the smaller scale must not only be included but they must abide by the same physical and mathematical interpretation, in order to avoid inconsistencies when making connections with those at the larger scale where dissipations are eminent.Three fundamental Problems I, II, and III are stated. They correspond to the commonly used service conditions. Reference is made to a Representative Tip (RT), the location where energy absorption and dissipation takes place. The RT can be a crack tip or a particle. At the larger size scales, RT can refer to a region. Scale shifting of results from the very small to the very large is needed to identify the benefit of using multiscale materials.