温度对TiAl合金及SiC配副摩擦磨损性能的影响

通过对TiAl合金与SiC配副在20,300和600℃下的摩擦磨损性能研究,分析了摩擦系数,磨损率和磨损形貌随温度的变化规律,探讨了磨损机制。结果表明:在实验温度条件下,TiAl合金的磨损率随温度的增大而增大。在20℃下TiAl合金主要为犁削磨损、磨粒磨损,随着温度的升高,出现氧化磨损,当温度增加到600℃时,氧化磨损严重;而SiC配副在20℃下的磨损率显著高于300及600℃下的磨损率,这是由于随温度的增加,SiC球的破坏机制由沿晶断裂向剝层磨损转变。     

不同成分对C/C-SiC材料摩擦磨损行为的影响与机理

采用温压-原位反应法制备C/C-SiC复合材料,研究了SiC、石墨和树脂炭成分对C/C-SiC材料摩擦磨损行为的影响及其机理.结果表明:SiC在摩擦表面摩擦膜的形成过程中起骨架作用,提高SiC的含量有利于提高摩擦系数,降低磨损率;树脂炭在材料中具有粘结各成分和提高摩擦系数的作用,但其成膜性较差,易增大磨损率;石墨粉在制动过程中起润滑作用,适量石墨粉有助于形成稳定的摩擦膜降低磨损率;摩擦表面摩擦膜的形成有利于减少C/C-SiC材料的磨损率.     

EM42与TC4干摩擦磨损性能的研究

在MMW-1高温高速摩擦试验机上进行M42高速钢的高速干滑动摩擦磨损试验。利用SEM观察并分析磨损形貌及磨损机理。结果表明:M42高速钢在与TC4钛合金配副干摩擦条件下,随着摩擦速度的增加,摩擦因数和磨损率先降低后升高。当摩擦热累积达到一定值后,摩擦表面产生严重塑性变形甚至形成润滑薄膜。随着载荷的增加,摩擦表面起初产生犁沟磨损、磨粒磨损和粘着磨损,形成转移润滑膜,该膜厚度增加并被带走脱落;摩擦系数先降低然后升高,磨损率随着载荷的增加而逐渐上升。     

IC-6高温合金及其防护性涂层的摩擦特性

采用电弧离子镀技术在IC－高温合金上沉积NiCrAlY涂层。研究了NiCrAlY涂层及IC－6高温合金在室温和600℃空气中无润滑状态下，以K17高温合金为摩擦副的摩擦特性。采用带有能谱的扫描电镜（SEM／EDX）分析IC－6高温合金和NiCrAlY涂层磨损表面的形貌和成分。实验结果表明，室温条件下摩擦时，一些碎屑从K17合金上脱落下来，在IC－6合金及NiCrAlY涂层表面上形成磨粒，随着摩擦时间延长，磨损表面元素发生氧化。试样在环境温度在600℃摩擦时，NiCrAlY涂层的表面比较快的形成氧化膜，减少金属－金属间的直接接触。环境温度升高后，摩擦表面温度也随之升高，氧化物的粘滞性增强，600℃时，合金和涂层摩擦系数都有不同程度的减小。     

软/硬质摩擦偶件材料对Ni3Al基涂层宽温域内摩擦学行为的影响

目的 合理选用摩擦偶件材料,以减缓Ni3Al基涂层宽温域内的摩擦磨损.方法 分别以WC-Co和316L为摩擦偶件,研究25～800℃内其对Ni3Al基涂层润滑和磨损机理的影响.采用高温硬度仪测试摩擦偶件在不同温度时的硬度,采用附带能谱仪的扫描电子显微镜观察磨损表面、磨斑和磨屑的形貌并测试成分,采用拉曼散射仪测试磨损表面和磨斑的成分.结果 在25～800℃,随温度的升高,两种摩擦副的摩擦系数具有一致的变化规律.与WC-Co对摩时,涂层在各温度下均具有低磨损率,且随温度升高,磨损率呈下降趋势.在25～200℃,与316L对摩时,涂层主要表现为粘着磨损和磨粒磨损,而与WC-Co对摩时,涂层在高接触应力下发生塑性变形,抑制Ag润滑相析出和涂层剥落,使其较前者具有高摩擦系数和低磨损率.在400℃,与WC-Co对摩时,高接触应力下产生的摩擦热促使涂层发生轻微的氧化,形成NiO和NiCr2O4,使其减摩性能优于Ni3Al/316L摩擦副.在600～800℃,与316L对摩时,涂层由严重的粘着磨损转变为氧化磨损;而与WC-Co对摩时,涂层由氧化磨损和剥层磨损转变为氧化磨损.此外,800℃时,Ni3Al/316L摩擦副的摩擦磨损发生在光滑润滑膜与粗糙转移膜之间,而Ni3Al/WC-Co摩擦副发生在光滑的润滑膜与转移膜之间.结论 在25～800℃,涂层与316L和WC-Co对摩时均具有良好的减摩性能,且与WC-Co对摩时具有更优的耐磨性能.     

摩擦速度和加载载荷对时效态Al-Sn-Cu合金摩擦磨损性能的影响（英文）

研究在油润滑状态下摩擦速度和加载载荷对时效态Al-Sn-Cu合金摩擦磨损性能的影响。结果表明:由于峰时效合金较欠时效和过时效合金具有最佳的强度-塑性配比和更高的硬度,因此峰时效合金表现出最优的摩擦磨损性能。摩擦速度和加载载荷对合金磨损率和摩擦因数具有显著影响。随着摩擦速度的增大,磨损表面的润滑膜和Sn相更为均匀,合金的磨损率和摩擦因数均降低;然而随着加载载荷的增加,均匀的润滑膜和Sn相被严重破坏,合金磨损率急剧上升。Sn相和包括中间润滑层、摩擦氧化层的润滑膜是影响Al-Sn-Cu合金摩擦磨损性能的决定性因素。     

TiNi60合金在油润滑下的超滑行为(英文)

研究了4种润滑油(蓖麻油、菜籽油、透平油、石蜡油)对TiNi60合金润滑性能的影响。研究发现,TiNi60合金在可再生蓖麻油润滑下呈现出摩擦因数为0.008的超滑现象。TiNi60合金在干摩擦及4种润滑油下的销-盘摩擦磨损实验研究表明:TiNi60合金在油润滑下具有优异的摩擦学性能,蓖麻油的润滑性能最优,摩擦因数最小,长时间摩擦后摩擦副表面无可测磨损。超滑机理归纳为极性高、碳链长的蓖麻油在TiNi60合金表面形成了边界润滑膜以及摩擦诱发的解离—OH基团形成屏蔽表面有关。     

不同载荷下镍基自润滑耐磨复合涂层的摩擦磨损性能

为了拓展所制备的镍基自润滑耐磨复合涂层的应用领域,基于前期研究基础,在HT-1000型高温摩擦磨损试验机研究涂层在300℃不同载荷下的摩擦磨损行为,利用SEM和EDS对磨损表面进行了形貌观察与成分分析,研究其摩擦磨损机理。结果表明:该复合涂层的摩擦系数及磨损率都随着载荷的增大呈现先减小后略增大的趋势;当载荷较低(2 N)时,涂层的磨损表面出现少量分散的磨屑;在中等载荷(5 N)下,磨损表面光滑平整,涂层中的润滑颗粒被挤压出磨损表面形成润滑膜,导致涂层具有良好摩擦磨损性能;随着载荷的增大,达到10 N时,磨损表面出现犁沟及部分由于硬质相碳化物和润滑颗粒剥落而形成的凹坑。     

不同温度下NiAl-2.5Ta-7.5Cr-1B合金组织及摩擦性能研究

以NiAl-2.5Ta-7.5Cr-1B合金为研究对象,分析了合金在不同温度下的摩擦磨损性能。通过对试样在不同温度下摩擦系数、磨损体积损失、腐蚀产物微观组织形貌及成分的表征,揭示了不同温度对NiAl合金的磨损性能影响规律。结果表明,随着温度升高,合金表面形成陶瓷润滑膜,合金的耐磨性提高。     

含MoS2镍基合金高温磨损机理

用粉末冶金方法制备了镍基复合材料,在销盘式高温磨损试验机上研究了其从室温到600℃的磨损行为,采用XRD和光学显微镜等对试样磨损表面和磨屑的形貌、成分和结构进行了分析,探讨了镍基复合材料的高温磨损机理.结果表明:在室温下由于摩擦过程中材料产生晶粒细化,材料具有一定的抗磨减摩性能;200℃时,摩损表面氧化变软,没有成膜润滑能力,摩擦学性能与室温相比,没有太大的变化,材料表现为轻微的粘着磨损和塑性变形;600℃高温摩擦时,承载表面及磨屑中的氧化物、钨酸盐及残余硫化物的高温软化或熔化的协同作用,在表面形成润滑膜,改善了材料的润滑性能,摩擦因数明显降低,材料的磨粒磨损和不断氧化导致磨损增加.     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.