Formation of nanocrystalline AZ31B Mg alloys via cryogenic rotary swaging

A bulk nanocrystalline AZ31B Mg alloy with extraordinarily high strength was prepared via cryogenic rotary swaging in this study.The obtained alloy shows finer grains,higher strength,and a negligible tension-compression yield asymmetry,compared with that prepared via room-temperature rotary swaging.Transmission electron microscopy investigations showed that at the initial stage,multiple twins,mostly tension twins,were activated and intersected with each other,thereby refining the coarse grains into a fine lamellar structure.Then,two types of nanoscale subgrains were generated with increasing swaging strain.The first type of nanoscale subgrain contained twin boundaries and low-angle grain boundaries.This type of subgrain appeared at the twin-twin intersections and was mainly driven by high local stress.The second type of nanoscale subgrain was formed within the twin lamellae.The boundaries of this type of subgrain did not contain twin boundaries and were transformed from massive dislocation arrays.Finally,randomly oriented nanograins were obtained via dynamic recrystallization,under the combined function of deformation heat and increased stored energy.Compared with room-temperature rotary swaging,cryogenic rotary swaging exhibits a slower grain refinement process but a remarkably enhanced grain refinement effect after the same five-pass swaging.

旋转锻造连接工艺研究

为了解决焊接性能差的材料间的连接问题,提出了一种利用旋转锻造工艺进行管材-管材、管材-棒料连接的新方法,并进行了旋转锻造连接过程的有限元分析和试验研究,揭示了旋转锻造连接过程的材料流动规律,得到了影响连接头强度的工艺参数。试验设备为自主研发的基于能量控制的小型旋转锻造设备,材料为T2铜管、6061铝管及塑料棒。对旋转锻造连接成形过程进行了有限元分析,得到了材料流动情况和连接工艺参数。结果表明:旋转锻造连接工艺可以形成稳定连接头;连接长度越小,连接头越容易被拉脱;径缩量是影响连接头强度的主要因素,在一定范围内随着径缩量的增加,连接强度不断增加;径缩量过大时,内管将在旋转锻造过程中发生破裂,无法形成连接头;试验结果表明,径缩量为0.8 mm时,铜管-铝管连接头强度达到铝管强度的62%,铜管-铜管连接头强度达到内铜管强度的68%,铜管-塑料棒连接头强度达到塑料棒强度的63%。

旋转锻造加工高比重W-Ni-Fe合金的退火工艺研究

使用粉末冶金工艺制备Ni/Fe为7∶3的W-Ni-Fe高比重钨合金,在使用旋转锻造方法进行形变强化后进行热处理。结果表明,锻造态W-Ni-Fe合金经过一定温度的锻后退火,强度有所提高,而塑性下降。样品的强度在一定的退火温度和保温时间范围内能得到提升,更高温度和更高时间的保温会使样品强度下降。不同钨含量的W-Ni-Fe合金,强度提升最大的退火温度和时间条件不同。SEM图像显示,退火前样品钨颗粒因旋转锻造变形呈现长条状织构,退火后钨颗粒的形状无明显变化。这些现象说明,锻造变形的合金样品经过锻后退火发生应变时效现象,使强度得到提升。研究明确了不同钨含量的W-Ni-Fe合金最佳的锻后退火工艺参数。

Pipe reduction of miniature inner grooved copper tubes through rotary swaging process

A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging machine was reached by a constant pushing force. The deformation of grooves in pipe reduced section during rotary swaging was analyzed. The shrinkage and extensibility of pipe reduction were measured and calculated. Furthermore, four aspects, including outer diameter, surface roughness, extensibility and processing time of pipe reduction, which were influenced by the pushing force, were considered. The results show that the tube wall thickness increases gradually along the z-axis at sinking section. However, the outer diameters, surface roughness and micro-cracks at reduced section tend to decrease along the z-axis. Besides, the effect of variation in the pushing force on the extensibility is limited while an increase in the pushing force results in a decrease of surface roughness. Therefore, a large pushing force within the limit is beneficial to pipe reduction manufacturing during rotary swaging process.

旋锻变形量对钨合金组织及力学性能的影响

为了获得高性能钨合金,对93WNiFe钨合金进行旋锻变形加工,研究旋锻变形量对93WNiFe钨合金力学性能及组织的影响。结果表明,随着变形量的增加,93WNiFe钨合金组织中W晶粒由圆球状逐渐被拉长成长条状,室温抗拉强度随变形量的增加而增加,由982 MPa增加到1622 MPa,断后延伸率随变形量的增加快速降低,由35.5%下降到5.5%。当旋锻变形量小于15%时,随着变形量的增加,93WNiFe合金洛氏硬度快速增加,室温冲击韧性快速降低;当变形量大于15%后,合金洛氏硬度增加变缓,室温冲击韧性值降低变缓;当变形量为30%时,洛氏硬度最大为HRC 47.2,室温冲击韧性值最小为30.80 J·cm-2。未变形的烧结态93WNiFe合金断口形貌中存在少量W晶粒解理断裂、大量W–粘结相界面断裂、W–W界面断裂和粘结相韧窝断裂;随着锻造变形量的增加,断口形貌中W晶粒解理断裂数量逐渐增加,W–粘结相界面断裂、W–W界面断裂和粘结相韧窝断裂数量逐渐减少。

Gd对冷旋锻制备纳米晶镁合金的影响

通过显微硬度测试、拉伸试验和透射电镜手段研究Gd元素对冷旋锻过程镁合金纳米化的影响。结果表明,由于纯镁中很难形成位错阵列,旋锻不能实现纯镁纳米化。相比之下,单独添加Gd,旋锻后镁合金晶粒可得到显著细化。在旋锻早期阶段,纯镁和Mg−Gd合金中都形成孪晶片层。随着增加旋锻变形的继续,相比纯镁,更多的非基面位错在Mg−Gd合金中形成,这促进了Mg−Gd合金中位错阵列的形成,导致合金纳米化。随着Gd含量的增加,Mg−Gd合金晶粒细化效果显著提升,晶粒细化至100 nm以下的临界Gd含量约为5.4%(质量分数)。

FEA modeling of effect of axial feeding velocity on strain field of rotary swaging process of pure magnesium

A coupled thermal-mechanical model of the rotary swaging of pure magnesium was developed using the general finite-element software program MSC/Marc to visualize the effect of axial feeding velocity on the rotary swaging process. The radial displacement occurring in one pulse impact increases in proportion to axial feeding velocity (vax). When the other processing parameters are fixed, the surface roughness of the swaged bar increases with vax and is in parabolic relation with vax. There exists a minimum velocity vax, min below which the decrease of vax will no longer improve the surface roughness. Under the technological conditions of this simulation, when the finial diameter d=6.6 mm, vax, min=1.82 m/min, and when d=7.0 mm, vax, =1.83 m/min. If min Ra=3.2 is required for the end product, then vax, =6.02 m/min is gotten for d=6.6 mm and vax, max max =7.05 m/min for d=7.0mm. The increase of vax has no notable influence on strain distribution along radial direction. The errors between the experimental and simulated height of the spiral spine-like ridges are below 8.0%.

Bulk and local textures of pure magnesium processed by rotary swaging

Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.

Effects of reduction of diameter on microstructure and surface roughness of rotary swaged magnesium by FEA

Combining the processing maps with FEA,the critical values of reduction of diameter(ΔR) for the appearance of as-cast microstructure,dynamic recrystallization grains and twins in the swaged magnesium were respectively studied,by which the rational range ofΔR was obtained.To ensure that the as-cast microstructure wouldn't be retained in the rotary-swaged magnesium,ΔR should be larger than 0.25 mm.To avoid the appearance of twins in the microstructure of rotary-swaged magnesium,ΔR should be less than 1.0 mm.ΔR should be between 0.25 mm and 1.0 mm to ensure the appearance of recrystallized grains.The surface roughness of rotary-swaged magnesium increases with the increase ofΔR by quadratic function.The simulated results accord well with the experimental data.In the process control of rotary-swaging(RS),ΔR should be maximized between 0.25 mm and 1.0 mm on the precondition that the requests for surface roughness have been satisfied.

Parametric Analysis on the Optimal Dimensions of Steel Sleeve in Swaging Type Anchorage for CFRP Tendon

This paper presents the parametric analysis conducted to derive the optimal dimensions of the steel sleeve necessary to secure the bond performance of the swaging type anchorage for CFRP tendon with diameter of 5 mm. To that goal, finite element analysis is performed on the parameters determining the dimensions of the sleeve like the thickness and inner diameters of the sleeve. The results show that a constant swaging pressure of about 450 MPa on the mean is distributed in the sleeve when the thickness ratio of the stress relief zone to the effective swaging zone of the sleeve is larger than 1.1 and that the swaging pressure tends to reduce linearly as much as this thickness ratio becomes smaller than 1.1. The pressure varies within a range of about 30% according to the change in the inner diameter of the sleeve whereas varies within a range less than 10% according to the change in the inner diameter when the thickness ratio is larger than 1.1. Finally, the optimal dimensions of the steel tube sleeve enabling to secure an anchor force larger than the rupture strength of the CFRP tendon with diameter of 5 mm are determined based upon the results of the parametric analysis.

Structure,mechanical characteristics,biodegradation,and in vitro cytotoxicity of magnesium alloy ZX11 processed by rotary swaging

Rotary swaging(RS)of alloy Mg-1.03Zn-0.66Ca(ZX11)was shown to refine the average grain size to 4.5±1.2μm in a longitudinal section and 4.8±0.9μm in a transverse section.In addition,a small amount of Mg2Ca particles about 300nm in size and Mg6Zn3Ca2 particles with a size of about lOOnm was detected.This resulted in pronounced strengthening:the yield strength and the ultimate tensile strength rose to 210±8 MPa and 276±6 MPa,respectively,while the elongation hardly decreased(22.0±1.8% and 18.3±2.9% before and after RS).Furthermore,RS led to an increase in the fatigue limit of the alloy from 120 MPa to 135 MPa and did not impair its resistance to chemical corrosion.The studies in vitro showed that ZX11 induces hemolysis without inhibiting the viability of peripheral blood mononuclear cells and has a more pronounced cytotoxic effect on tumor cells in comparison with non-transformed cells.No significant difference of the latter effect between the initial and the deformed states was observed.

Plastic forming behavior of axisymmetric bimetal products with rotary swaging

In this paper,an elasto-viscoplastic three-dimension(3D) finite element model is developed to simulate the processing of bimetal tube with rotary swaging. Through simulation,the effects of high-frequency pulse stroking on the distribution and histories of stress,stain and loading are clarified. The stress in inner tube is compressive and higher than the minimum bonding force. Meanwhile,the stiffness of inner tube impacts outer tube extension in length.

EBSD characterization of recrystallization microstructure of cold-swaged Ti-23Nb-0.7Ta-2Zr-O alloy

The microstructures of the cold-swaged and recrystallized Ti-23Nb-0.7Ta-2Zr-O(TNTZO)(mole fraction,%) alloy were investigated by electron backscatter diffraction(EBSD). The difference in microstructure,texture and recrystallization process was evaluated between the TNTZO alloy and traditional body centered cubic(bcc) metals. The results show that the cold-swaged TNTZO alloy presents a pronounced 〈110〉fiber texture in the axial direction. The recrystallization of the TNTZO alloy is achieved by the nucleation of new grains and the growth of these new grains at the expense of the deformed structure. The TNTZO alloy behaves a very similar way to traditional bcc metals in the features of the microstructure,texture and recrystallization.

Preparation of nanocomposite thoriated tungsten cathode by swaging technique

By using the high energy ball milling method, the nanosized ThO 2 powders were obtained. Through mixing powders, sintering and hot swaging processing, a nanocomposite thoriated tungsten cathode was fabricated. The relative density of the nanocomposite material is near 100%. The microstructure of nanocomposite cathode is quite different from that of conventional thoriated tungsten cathode. Most of thoria particles are less than 100?nm in diameter, and distribute on the boundaries of tungsten grains. The nanocomposite cathode shows a much lower arc starting field than that of conventional cathode, which will improve the performance of the cathode significantly.

翼子板门轴侧棱线不顺问题的解决方法

从制件造型、结构设计、工艺排布方案、模具结构设计、模具零件加工策略及装配调试等方面阐述了翼子板门轴侧棱线不顺问题产生的原因,并结合实例,分析翼子板模具开发各阶段关键技术要求以及制件设计时如何规避棱线不顺问题,为解决类似问题提供参考。

高速线材裂纹原因分析与控制

对鞍钢股份有限公司线材厂2#线近几年来生产盘条产生裂纹的原因进行了分析,发现坯料遗传、轧辊缺陷、导卫刮磨和轧槽充满是导致裂纹产生的主要原因。通过采用细化钢坯裂纹标准、精准控制轧辊使用、改变导卫摩擦方式、细化铁型尺寸等控制措施,2022—2023年2#线生产作业区生产冷镦钢开裂率降低15%,初验合格率达到95%以上,废次降率达到0.5%,弹簧钢表面裂纹可控制在30μm以下,产线过程控制能力有效提高。

户用SBR一体化设备处理农村分散式污水的应用

针对农村生活污水排放不规律、排水量小、污染物浓度高、难收集等特点,提出了采用户用SBR一体化设备处理分散式农村生活污水,处理规模为0.3 m 3/d。运行结果表明:该设备运行稳定、抗冲击能力强、能耗低,吨水运行成本低至0.5元/m 3;对污染物去除效果好,出水COD平均浓度30.86 mg/L,NH 3-N平均浓度1.45 mg/L,TN平均浓度30.29 mg/L,出水水质稳定达到《农村生活污水处理设施水污染物排放标准》(DB11/1612-2019)三级标准:COD≤100 mg/L,NH 3-N≤25 mg/L。户用SBR一体化设备运行成本低,对农村低碳氮比废水的脱碳脱氮效果良好,且具有较强的抗冲击负荷能力,可为分散式农村生活污水处理提供参考。

支持向量机在污水处理厂出水COD预测中的应用

随着城市化的进行和经济的快速发展,城市居民用水量呈逐年递增趋势。城市污水处理过程中由于水力停留时间过长等,难以实时掌握污水水质情况。化学需氧量(COD)是衡量污水水质的重要指标之一,通过有效监测出水COD的波动,可实现污水处理过程在线管控。通过收集某城镇污水处理厂进水、出水历史数据(COD、pH、溶解氧、氨氮等),利用支持向量机SVM(Support Vector Machine)、K近邻算法(K-Nearest Neighbor,KNN)等人工智能算法建立数学预测模型,实现了对出水COD指标的有效预测。

基于ABAQUS的永久式径向挤压管接头的密封性能研究

航空管接头是一种基础的管路连接件,广泛应用于飞机的液压、燃油和环控等系统中,并提供一定的耐压和密封能力,在飞机使用过程中常出现“跑、冒、滴、漏”等质量问题,对飞机的可靠性和安全性产生着重要影响。航空管接头可分为永久式管接头和可分离式管接头,其中永久式管接头是一类永久连接、不可拆卸式的管接头,重量和体积较小,且有较高的耐压能力和可靠性,在民用飞机中广泛应用。通过介绍一种国外先进的永久式径向挤压管接头,进行结构设计和样件试制工作,运用ABAQUS有限元分析软件对其压接工艺过程和密封原理进行仿真分析,并按照AS4459B的标准要求,开展了静态和动态性能试验验证。

管端收口对特殊螺纹石油套管性能的影响

Φ114.30 mm×7.37 mm P110特殊螺纹套管经过管端收口加工后,管体力学性能试验和接头气密封评价试验结果表明,经过管端收口加工后的产品的力学性能依然满足API Spec 5CT要求,且顺利通过了ISO 13679实物评价试验。证明经过一定变形量的管端收口处理后的特殊螺纹套管的使用性能满足设计要求,可以满足油田复杂井况的应用要求。