钛合金材料OIM试样的电解抛光及制备工艺

由于钛合金材料强度硬度较高，机械抛光通常不能去除试样表面的残余应变层，因而采用电解抛光是制备电子背散射衍射试样的理想方法。本研究通过正交试验进行优选，并对优选的电解抛光工艺参数进行调整，制定出了钛合金电子背散射衍射试样的快速制备工艺。     

Effect of flexibility of the femoral stem on bone-remodeling and fixation of the stem in a canine total hip arthroplasty model without cement

The purpose of this study was to compare, with regard to fixation of the implant and femoral bone resorption, two fully porous-coated stems of different stiffnesses in a canine total hip arthroplasty model. A bilateral arthroplasty was carried out with insertion of a titanium-alloy stem (which had stiffness properties comparable with those of the canine femur) on one side and with insertion of a composite stem (which was three to fivefold more flexible than the canine femur) on the contralateral side. Eight femora were evaluated at six months and eight, at eighteen months after the operation, to determine the extent of bone ingrowth, periprosthetic cortical area, intracortical porosity, and bone-remodeling. Despite the markedly greater flexibility of the composite stems, no significant difference could be detected (with the numbers available), with regard to the overall degree of femoral stress-shielding, cortical area, or cortical porosity, between these stems and the stiffer, titanium-alloy stems at either time-period. However, the composite stems had less bone ingrowth and more formation of radiopaque lines than did the titanium-alloy stems. At eighteen months, the values for bone ingrowth were 9.7 +/- 5.38 percent (mean and standard deviation) for the composite stems compared with 28.1 +/- 5.31 percent for the titanium-alloy stems (p = 0.003). Furthermore, the histological sections from the femora containing a composite stem showed radiopaque lines indicative of fibrous ingrowth approximately threefold more often than did those from the femora containing a titanium-alloy stem (p = 0.02).     

Polyethylene wear after total hip arthroplasty: the effect of a modular femoral head with an extended flange-reinforced neck

The use of modular components in total hip arthroplasty has been thought to contribute to accelerated polyethylene wear. Specifically, a modular femoral head with a flange extension and a longer neck may cause increased wear. The purpose of the current study was to evaluate the effect of a flange extension on polyethylene wear. Ninety-one patients who had had a total of 100 primary total hip arthroplasties were evaluated after an intermediate duration of follow-up. All of the acetabular components consisted of a hemispherical titanium-alloy fiber-mesh porous-coated shell with a nonelevated modular polyethylene liner; they were inserted without cement and with use of supplemental screws through the dome after so-called line-to-line reaming. All of the femoral components consisted of a modular head with a diameter of twenty-eight millimeters and either a long neck (with a flange extension) or a short or medium neck (without a flange extension). The study group comprised sixty-two patients (sixty-six hips) who had had radiographic evaluation that was adequate to allow the valid measurement of polyethylene wear. Thirty-two hips were in men, and thirty-four were in women. The mean age of the patients was fifty-six years, the mean weight was seventy-three kilograms, and the mean duration of follow-up was 6.1 years (range, four to eight years). The rate of polyethylene wear in the eleven hips in which the femoral component had a flange extension was significantly greater than that in the fifty-five in which the femoral component did not have a flange extension (mean, 0.17 compared with 0.11 millimeter per year; p = 0.009). Multivariate analysis showed that the presence of a flange extension was associated with increased polyethylene wear to a greater degree (F = 2.86) than were all other variables that were measured, including a younger age (F = 1.72), a more vertical angle of the acetabular component (F = 0.49), a heavier weight (F = 0.14), male gender (F = 0.11), and a smaller initial thickness of the polyethylene (F = 0.02). These data support an association between the presence of a modular femoral head with a flange extension and an accelerated rate of polyethylene wear. The presumed mechanism is an increase in peripheral, or so-called rim, impingement of the flange-reinforced neck on the acetabulum due to a decrease in the ratio between the diameters of the femoral head and neck.     

金纳米粉末的制备与特性

应用超声辅助电解法制备金纳米粉末.电解液由柠檬酸三钠、硫酸钠组成;金箔作阳极,钛合金杆作阴极;钛合金杆作为超声波放大转换器与20kHz的超声波源相连接.由于超声波的空化效应,在阴极形成金聚集体将分散到电解液中,这样通过控制电流密度、超声波脉冲的周期和幅度就可以获得直径约为50nm左右的面心立方结构(fcc)的金纳米粉末.利用透射电镜(TEM)、X射线衍射(XRD)、X射线光电子谱,表征了金纳米粉末的结构、形貌及其化学组分.     

Hardening VT6 alloy by electroplastic rolling

Electroplastic rolling may be used to produce VT6 titanium-alloy sheet with ultrafine-grain structure and improved performance. The influence of the true strain on the structure and mechanical properties of the alloy is studied.     

Determination of hydrogen in titanium alloys by cold neutron prompt gamma activation analysis

Cold neutron prompt gamma-ray activation analysis (CNPGAA) has proven useful for the analysis of hydrogen in titanium alloys. The analysis is nondestructive, measures the entire sample, and the results are independent of the chemical form of hydrogen present. We have used the technique to measure H mass fractions as low as 50 mg/kg in titanium-alloy jet-engine compressor blades and to measure hydrogen in standards for neutron tomography.     

Design and optimization of deformation modes in titanium shells under superplastic conditions

Titanium-alloy shells are now commonly used in the fabrication of aerospace structures. A design method to determine optimum manufacturing techniques for molding such shells has been developed. This method is based on an analysis of the behavior of the critical cross sections in deformable titanium-alloy shells. Based on materials from a paper presented at the 7th International Scientific and Technical Conference “Aerospace Technologies-2006” held in Voronezh, September 13–15, 2006. __________ Translated from Metallurg, No. 2, pp. 26–30, February, 2007.     

Restoring the single lower incisor implant with esthetics, antirotation, and retrievability

The long-term success of restoring the lower incisor implant is partially dependent on retrievability of all components down to the implant. Because this implant is usually placed vertically or buccally in the bone, the ability to achieve esthetics without seeing the screw access hole becomes critical. The emergence profile of the crown overlying the implant fixture ultimately dictates the esthetics. The single crown can also become loose during function and, therefore, antirotation of the abutment is imperative. The Octa-Hex Implant Restoration System presents an alternative method of achieving gingival seal with a titanium-alloy connector to the implant, emergence profile with a custom-fabricated casting on this connector, antirotation from intimate contact with implant indexing, and retrievability by a fixation screw and cementation. With the lower incisor, this system offers retrievability without the screw access hole affecting esthetics.     

Influence of the stress state on the structure and properties of welded steel and alloy structures

The residual stress due to welding in steel and alloy structures is analyzed. The greatest residual stress is produced by cooling of the welded structure. The results of calculations are in satisfactory agreement with the experimental deformation of the structure in welding on a test bench. The tests reveal the direction of the internal stress and permit assessment of the geometry of parts on the basis of a model of the temperature fields in the butt welding of steel and titanium-alloy workpieces. A coercimeter may be used to assess the stress state of the material and its defect content. By that means, it is possible to predict the structural state and properties of weld joints. The dynamics of welding deformation may be understood on the basis of the internal residual stress and the structural transformations produced by the welding process.     

Detection of stress concentrators by means of acoustic emission

The influence of the concentration on the damage to titanium alloys is studied. Samples of OT4 titanium alloy (α class) and VT3-1 titanium alloy (α + β class) with stress concentrators of different radii are investigated. The influence of stress concentration on the acoustic emission is assessed for samples with different radii. The volume of material involved in deformation is plotted as a function of the distribution of the maximum local stress, and the distribution of the basic acoustic-emission parameters is determined as a function of the nominal destructive stress for OT4 and VT3-1 titanium-alloy samples with different stressconcentrator radii. The influence of the stress concentration α on the damage to OT4 and VT3-1 titanium alloys is studied theoretically and experimentally. The results may be used for diagnostic systems to determine the least hazardous type of stress concentrator.     

Wear Mechanisms of High Chromium Iron Roll under Hot Rolling Conditions

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金刚石工具磨损形式的观察与分析

本文对金刚石工具的磨损进行了研究。扫描电镜观测表明，金刚石工具磨损包括轻微磨损和严重磨损两大类。轻微磨损包括金刚石的犁沟磨损、剥层磨损和点蚀磨蚀等形式；严重磨损包括金刚石碎裂磨损、胎体与金刚石界面挤出与离隙和整体脱粒等形式。分析了各种磨损形式产生的原因和机理，指出金刚石工具的出刃高度ｈ随轻微磨损而减小，却随严重磨损而增大。金刚石的严重磨损虽然可以提高磨削效率，但却影响工具的使用寿命。     

Selection of Heat Treatment Process and Wear Mechanism of High Wear Resistant Cast Hot-Forging Die Steel

 Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50-300 N at 400 ℃ by a pin-on-disc high-temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS); wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1120 ℃, then decreased at up to 1220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order: 700 ℃ (tempered sorbite), 200 ℃ (tempered martensite), 440 to 650 ℃ (tempered troostite). An appropriate combination of hardness, toughness, microstructural thermal stability was required for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1120 ℃, quenched in oil, then tempered at 440 to 650 ℃ for 2 h.     

热轧带钢平整机工作辊磨损规律

 由于工艺和结构的特殊性,带钢热轧平整机的工作辊磨损演变规律与热连轧过程有显著差别。然而,目前对工作辊磨损的研究主要集中在热轧,对热轧平整机磨损演变规律的研究较少。为此,从热轧平整机工作辊的磨损特点出发,结合现场大量实测磨损数据,分析磨损的形成与发展机理。通过ABAQUS有限元仿真分析软件建立单机架四辊热轧平整机的辊系-轧件耦合计算模型,揭示不同磨损阶段工作辊接触应力对磨损演变的作用规律。通过与某厂1 580 mm热轧平整机的实际数据对比,结果表明,工作辊磨损演变规律能够准确地反映实际生产过程的磨损情况,为热轧平整机轧辊磨损理论的发展与磨损预报模型的进一步优化奠定了基础。     

Effect of Alloying Elements on Thermal Wear of Cast Hot-Forging Die Steels

The effect of main alloying elements on thermal wear of cast hot-forging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wear of cast hot-forging die steels. The wear rates decrease with an increase in chromium content from 3% to 4% and molybdenum content from 2% to 3%, respectively. With further increase of chromium and molybdenum contents, chromium slightly reduces the wear resistance and molybdenum severely deteriorates the wear resistance with high wear rate. Lower vanadium/carbon ratio （1.5-2.5） leads to a lower wear resistance with higher wear rate. With an increase in vanadium/carbon ratio, the wear resistance of the cast steel substantially increases. When vanadium/carbon ratio is 3, the wear rate reaches the lowest value. The predominant mechanism of thermal wear of cast hot-forging die steels are oxidation wear and fatigue delamination. The Fe2O3 and Fe3O4 or lumps of brittle wear debris are formed on the wear surface.     

M50NiL轴承钢渗层碳化物特征与滑动磨损行为的研究

摘要：研究了M50NiL轴承钢在不同磨损时间和外加应力作用下的磨损行为和机制。结果表明：渗碳层组织为孪晶马氏体和近球状MC、M23C6和棒状M2C型碳化物。外加应力对钢的磨损形式与形貌具有显著影响，钢的磨损形式为轻微粘着磨损和磨料磨损，摩擦因数较快保持稳定到0.02。延长磨损时间对钢的磨损性能与机制具有明显作用，磨损时间达到3万s，MC、M23C6、M2C脱落，部分碳化物破碎形成磨料磨损。磨损时间与外加应力耦合作用显著影响钢的磨损性能与质量，磨损时间为3000s，外加应力由0306MPa增至1530MPa，碳化物导致磨料磨损，磨损质量由025mg增至038mg；外加应力增至2142MPa，更多大尺寸碳化物脱落，导致钢的摩擦因数逐渐升高至0037，磨损质量达到033mg。     

Research on carbide characteristics and sliding wear behavior of carburized layer of M50NiL bearing steel

The wear behavior and wear mechanism of M50NiL bearing steel under different wear times and applied stresses were studied. The results show that the microstructure of the carburized layer is composed of twin martensite, nearly spherical MC, M23C6 and rod like M2C carbides. The applied stress has a significant effect on the wear form and morphology of steel. The wear forms of the steel are slight adhesive wear and abrasive wear. The friction coefficient of the steel keeps stable to 002. Prolonged wear time has an obvious effect on the wear property and mechanism of steel. When the wear time reaches 30000s, MC, M23C6 and M2C carbides rub off. Some carbides are broken and subsequently formed abrasive wear. The coupling effect of wear time and applied stress significantly affect the wear property and quality of steel. When the wear time is 3000s, the applied stress increases from 0306MPa to 1530MPa. The wear weight loss increases from 025mg to 038mg due to carbides abrasive wear. When the applied stress increases to 2142MPa, large scale carbides rub off. This leads to the increasing of the friction coefficient to 0037 and the wear mass to 033mg.     

胞状碳硼化物对中锰钢耐磨性的影响

本文对奥氏体中锰钢、钒强化含胞状碳硼化物奥氏体中锰钢和钛强化含胞状碳硼化物奥氏体中锰钢在高应力和低应力条件下相对耐磨性进行了测定。结果表明,在低应力叶片式磨料磨损条件下,两种含硼中锰钢的相对耐磨性显著高于奥氏体中锰钢;而在高应力的冲击式磨料磨损条件下,前者的相对耐磨性则明显低于后者。结果说明,引起三种钢耐磨顺序的变化的主要原因是低应力条件下的磨损机制与高应力条件下的磨损机制不同。低应力下以表面疲劳剥落为主,高应力下以犁削,脆断为主。本文的试验结果也说明在低应力条件下以钛代钒来强化胞状硼化物,可获得更高的耐磨性和更大的经济效益。     

The wear behavior of nitrogen-implanted metals

The effect of nitrogen implantation on the wear behavior of a range of metals has been studied. Hardness measurements and pin-on-disc wear tests which characterize specifically the properties of the thin implanted layer have been carried out. It is shown that large improvements in wear resistance can be obtained by nitrogen implantation and that a loose correlation exists between reduced wear and increased surface hardness. However, it is demonstrated, on the basis of detailed examination of the wear tracks, that the best improvements in wear performance occur only when implantation produces a change in the dominant mode of wear. It is further shown that the formation of surface oxide layers during the wear process is often associated with these changes in wear behavior. The wear mechanisms, and the changes thereof, are described and discussed in detail for Ti-6Al-4V, hard chromium electroplate, and a range of ferrous alloys. Work was performed at BBC, Brown Boveri Research Center, CH-5405 Daettwil, Switzerland.     

新型耐高温磨损钢板组织性能与高温磨损行为研究

摘要：随着低合金耐磨钢应用领域逐渐增加,对其中高温条件下的耐磨性能提出了要求。通过成分设计、控制轧制和离线热处理工艺制备了一种Mo、V合金化新型低合金高温耐磨钢。初步探索了其在300~500℃温度范围的高温磨损行为和组织演变,并与同硬度级别的商用常规耐磨钢NM450进行了对比分析。结果表明：通过添加Mo和V等元素可以抑制位错密度降低、板条合并以及渗碳体析出、长大过程,提高了高温耐磨钢的高温强度等力学性能,从而提高了其高温磨损性能。300、400、500℃温度的磨损性能分别是常规NM450的1.5、1.4和2.2倍左右。300到500℃的磨损机制由磨料磨损向氧化磨损和塑性变形转变。高温耐磨钢高温屈服强度相对更高,塑性变形更小。