Deoxidation Behavior of Alloys Bearing Barium in Molten Steel

The deoxidation behaviors of alloys bearing barium in pipe steel were researched with MgO crucible under argon atmosphere in MoSi2 furnace at 1 873 K.The total oxygen contents of molten steel,the distribution,size and morphology of deoxidation products in the steel were surveyed.The metamorphic mechanism for deoxidation products of alloy bearing barium was also discussed.The results show that applying alloy bearing barium to the pipe steel,very low total oxygen contents can be obtained,and deoxidation products,which easily float up from molten steel,can be changed into globular shape and uniformly distributed in steel.The equilibrium time of total oxygen is about 25 min,and the terminal total oxygen contents range from 0.002 0%to 0.002 2% after treating with SiCa wire.The best deoxidizers are SiAlBaCa and SiAlBaCaSr.

A novel approach for evaluation of load bearing capacity of duplex coatings on aluminum alloy using PLS and SVR models

Duplex NiP/TiN coatings consisting of the electroless intermediate layers and the physical vapor deposition(PVD) top layers were fabricated on the AA6061 aluminum alloy in order to enhance the load bearing capacity. The main objective of this study was to model the load bearing based on the thickness, adhesion and elastic modulus of the coatings. For this purpose, partial least square(PLS) and support vector regression(SVR) approaches were employed.The results showed that both models had an acceptable performance;however, the PLS model outperformed SVR. The correlation coefficients between thickness, adhesion and elastic modulus with load bearing were 0.841, 0.8092 and 0.7657, respectively;so, thickness had the greatest effect on the load bearing capacity. The composition and structure of the samples were evaluated using XRD and SEM. The load capacity of the coated samples was also discussed based on the wear and adhesion evaluations. Dry sliding wear tests, under a load of 2 N and a sliding distance of 100 m,demonstrated the complete destruction of the coated specimens with low load capacity. The samples with high load capacity showed not only a superior tribological performance, but also a remarkable adhesion according to the Rockwell superficial hardness test.

Tribological behavior of three typical bearing alloys under influence of additives

The influences of lubricating additives on the tribological behavior of lead, tin, copper base bearing alloys-0.45%C steel rubbing pairs under the condition of boundary lubrication were researched. The results show that because of the difference of physical chemistry performance at bearing alloys and steel, some conventional lubricating additives which is beneficial to steel-steel rubbing pairs is harmful to these bearing alloys-steel rubbing pairs,and the wear volume can be increase by 7 times under the test condition. The measure results of contact resistance during the test process show that the higher the contact resistance at rubbing surface, the better the tribological behavior of tribo-system. Moreover for the lead base and tin base bearing alloys-0.45%C steel rubbed pairs, the thicker the compact oxide layer of steel surface, the larger the friction coefficient and wear volume, which demonstrates that oxidation wear plays an important part in the wear process.

Microstructural Features of Spray-Deposited Immiscible Bearing Alloys Al-43Sn and Al-7Sn-1.3Cu-1.3Ni

Two commercial grade aluminum based immiscible bearing alloys were spray-deposited using convergent-divergent type of nozzle. The processing parameters for spray-deposition were adjusted in such a way that most of the droplets arrived on the deposition substrate in either liquid or semi-liquid state. The microstructural features of spray-formed and as-cast alloys are compared. In spray-formed alloys equiaxed grains were observed. The cell boundaries and intercellular regions were observed to be decorated with sub-micron sized particles whereas in normal casting the second phase was observed to be segregated along grain boundaries. The morphology and distribution of second phase were observed to have similarity with those in over-spread and atomized powders produced under similar processing conditions. The microstructural features observed with variation in spray conditions are discussed in detail.

Preparation of Scandium Bearing Master Alloys by Aluminum Magnesium Thermoreduction

The new preparation method of scandium bearing master alloys, in which scandium oxide was fluorinated by reaction with NH 4HF 2 and then reduced by aluminum magnesium in fused salt containing alkali and alkaline fluoride under atmosphere, was studied. The effect of sorts of metallic reductive and technique conditions such as reducing temperature and time on the recovery of Sc was discussed. When the liquid aluminum magnesium was used as the reductive agent, the all recovery exceeds 80% and the concentration of Sc in master alloy prepared exceeds 1.9%. The best reducing reaction temperature and time are 1100 K and 40 min respectively. The newly produced Sc from reduction combines with Al to produce the stable compound Al 3Sc, so the reduction progress is sustained and the recovery of Sc is increased.

Microstructures and Mechanical Properties of Al-Zn-Sn Bearing Alloys for High Performance Applications

The mechanical behavior and indentation creep of Al-20 wt% Zn bearing alloy has been modified with adding 0.2 wt%, 0.5 wt%, 1 wt%, 1.5 wt% Sn. These bearing alloys were prepared by melt spinning technique. The scanning electron microscopy (SEM) was used to study the morphology of the melt spun alloys and x-ray diffractometer (XRD) for the identification of the phases pre- sent in these melt-spun bearing alloys. The results show that the structure of Al80-x-Zn20-SnX (X = 0.2%, 0.5%, 1% and 1.5%) bearing alloys is characterized by the presence of α-Al of FCC structure and SnZn intermetallic compound of anorthic structure. The Al-20Zn-1.5Sn has a smaller crystallite size and grain size as indicated from X-ray and SEM analysis respectively, which leading to the enhancement of the mechanical properties. The mechanical properties and indentation creep of these bearing alloys were studied by tensile test machine and vickers indentation testing at room temperature, respectively. The Al-20Zn-1.5Sn has higher hardness value and creep resistance than other alloys. This was attributed to the strengthen effect of Sn as a strong solid solution element in Al-matrix. The stress exponent values in the range 2.4 - 4.2 indicate that the grain boundary sliding is the possible mechanism during room temperature creep deformation of melt-spun Al-Zn-Sn bearing alloys.

Strengthening mechanism of steels treated by barium-bearing alloys

The deoxidation, desulfurization, dephosphorization, microstructure, and mechanical properties of steels treated by barium-bearing alloys were investigated in laboratory and by industrial tests. The results show that barium takes part in the deoxidation reaction at the beginning of the experiments, generating oxide and sulfide compound inclusions, which easily float up from the molten steel, leading to the rapid reduction of total oxygen content to a very low level. The desulfurization and dephosphorization capabilities of calcium-bearing alloys increase with the addition of barium. The results of OM and SEM observations and mechanical property tests show that the structure of the steel treated by barium-bearing alloys is refined remarkably, the lamellar thickness of pearlitic structure decreases, and the pearlitic morphology shows clustering distribution. Less barium exists in steel substrate and the enrichment of barium-bearing precipitated phase mostly occurs in grain boundary and phase boundary, which can prevent the movement of grain boundary and dislocation during the heat treatment and the deformation processes. Therefore, the strength and toughness of barium-treated steels are improved by the effect of grain-boundary strengthening and nail-prick dislocation.

高强度Al-Sn-Si-Cu-Mg轴瓦材料的研究

针对现代发动机向高速、重载、无污染方向发展的需求,研发出了一种新型高承载能力的、无Pb的铝合金轴瓦材料。通过正交试验,分析了添加元素对合金力学性能的影响规律,确定了合金的成分控制范围。试验结果表明:该合金具有显著的时效硬化能力,它在475℃0.5h固溶淬火、160℃8h时效后的性能指标可达HV≥70;抗拉强度Rm≥200N／mm2;伸长率A≥15％。

新型Al-Sn-Si-Cu-Mg轴瓦材料组织与性能研究

选择Al Sn Si Cu Mg合金作为研究对象,采用Leica光学显微镜、EPM810Q电子显微镜等手段观察分析Cu、Mg、Sn、Si形态分布规律,进而研究了加工工艺对合金组织性能的影响,同时提出高温短时退火制度,最终确定预处理工艺和退火制度,发现通过加工和热处理,可消除合金中Sn、Si晶间网状分布,从而改善合金的加工性能。

HAZ CRACKING AND HOT DUCTILITY OF Ni_3AI CONTAINING Zr ALLOY

The HAZ cracking test in EB welding condition and hot ductility test show that the cracking mechanism is the formation of Ni - Ni5Zr eutectic which is resulting from the enrichment of Zr in grain boundaries during welding.In order to eliminate HAZ cracks the diffusion and recrystalization anealing treatment after cast and during cold rolling should be conducted in vacuum or protecting atmosphere and at the same time a slow welding speed is necessary.

硬质颗粒TiC对Al-Sn-Cu合金性能影响研究

采用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析(EDS)以及硬度试验和摩擦磨损试验等方法,研究了TiC颗粒对Al-Sn-Cu合金组织、力学性能及摩擦磨损性能的影响,结果表明:添加TiC颗粒后该合金组织明显细化,平均晶粒尺寸由87μm降低至37μm,降幅达到57.4%;布氏硬度达到95.2 HB,比未添加TiC颗粒时提高了10.658%,抗拉强度提升了5.88%;在载荷200 N、主轴转速200 r/min、干摩擦试验条件下,Al-Sn-Cu-TiC合金材料的摩擦因数为0.345,比未添加TiC颗粒的合金(0.384)降低了10.16%;在载荷200 N、主轴转速200 r/min、油润滑试验条件下,Al-Sn-Cu-TiC合金材料的摩擦因数为0.027,比未添加TiC颗粒的合金(0.126)降低了78.57%。

Yixunite and Damiaoite—A Twin of New Native Alloys of Indium and Platinum from the Yanshan Mountains

Yixunite and damiaoite Were found in a cobalt- and copper-bearing platinum ore vein of a contact metasomatic deposit. The chief ore minerals are bornite, chalcopyrite, magnetite and carrollite. The platinum minerals include moncheite, sperrylite, daomanite, cobalt malanite and cooperite. Yixunite and damiaoite occur as immiscible globules, 1.0 to 2.0 mm in diameter. Yixunite is always in the central part of a globule. It is opaque with metallic lustre, bright white colour and black streak. HM = 5.8; VHN50 = 634 kg/mm2 (573-681 kg/ mm2); insoluble in HCl, HNO3, HF or H3PO4; no cleavage; no magnetism. Density is hard to measure because of small grain size. Calculated density = 18.21 g/cm3. Reflective colour is bright white with a yellowish tint. Isotropic. The mean analytical results (ranges) (%) are: Pt 82.8 (81.8-83.6), In 16.4(15.6-17.1) and total 99.2. The empirical formula (based on 4 atoms) is Pt2.993 In1.007 . The five strongest lines of X-ray diffraction (hkl, d,I) are 111, 2.30 (100); 200, 1.99 (60); 202, 1.411 (40);311, 1.203 (80); 222, 1.151(40). Space group: Pm3m with a =0.3988(3) nm and Z= 1. Damiaoite occurs as single globules or was exsolved from yixunite. Opaque with metallic lustre; bright white colour with black streak; HM = 5.3; VHN50 = 485 kg/mm2 (434-529 kg/mm2); insoluble in HC1, HNO3, HF or H3PO4; cleavage: no; magnetism: no. Density: hard to measure because of small grain size. Calculated density = 10.95 g/ cm3. Reflective colour is bright white with a yellowish tint. Isotropic. The mean analytical results (ranges) (%) are Pt 45.6 (45.4-46.0), In 53.5 (52.4-53.9), total 99.1. The empirical formula (based on 3 atoms) is Pt0.002 In1.998. The six strongest lines of X-ray diffraction (hkl.d,I) are 220,2.25 (100); 311,1.92 (60); 400,1.59 (60); 422,1.299 (80); 440,1.125 (60); 620,1.006 (70). Space group: Fm3m with a = 0.6364 (3) nm and Z = 4.

MICROSTRUCTURE AND PERFORMANCE OF Ni-Hf BRAZING FILLER ALLOY

In consideration of the envelopment of γ dendrites by the Hf-rich melts at the late period of solidification of the cast Ni-base superalloys containing Hf,a heat of brazing filler alloy composed of Ni-18.6Co-4.5Cr-4.7 W-25.6Hf(wt-%)was prepared.This alloy is hypereutectic.γ phase is the leading phase in eutectic γ+Ni_5Hf and γ bars are surrounded by Ni_5Hf phase.At the section perpendicular or parallel to the γ growing direction,the eutectic morphology is cellular or laminar respectively.The content of Ni_5Hf in the alloy is 68.7v.-%. The compositions of primary and eutectic Ni_5Hf are very similar.Ni,Co and Hf are the main elements and solubility of Cr and W in Ni_5Hf is very low.This alloy is an ideal brazing filler suitable to the directional or single crystal superalloy,and the elements are beneficial to superalloys properties.This filler alloy is of low melting point and of good fluidity.After braz- ing at 1240℃,5 min+1190℃,I h in 10^(-3) Pa vacuum,the microstructure of bond is the same as that of Hf-bearing superalloy.No Si and B contamination is involved.

SOLUTION TO THE STRESS DISTRIBUTION ON THE SURFACE LAYER OF BUSHING ALLOY BY COUPLING BEM WITH ELASTICITY METHOD

In the design of the fatigue strength of dynamically loaded bearing in the equipmentssuch as internal combustion engines and roimg mun, the solution to the stress distribution on thebushing alloy layer is an important and difficult problem. In this paper, a new method has beenproposed by coupling BEM with etheticity method, The algorithm and its implementation were deseribed in details The calculation results verify that this up-dated method can provide us a moresimple and effective tool for solvingthe fatigue stress of the bushing alloy with tangible benefit oftime-saving and high computation accuraey. It may open a new vista in bearing fatigue strength design.

粘铝合金板加固RC梁抗弯性能试验及正截面承载力

为了探讨铝合金板厚度与端部U形铝合金箍板构造对RC梁破坏机理及抗弯性能的影响,对16根铝合金板加固RC梁进行了4点弯曲静力加载试验。在试验梁底铝合金板的表面以及试验梁跨中截面的顶面、侧面粘贴应变片,在试验梁底跨中、梁顶两端支座布置百分表。为了推导铝合金板加固RC梁的正截面承载力计算式,基于试验得到的破坏机理,通过引入6个基本假定,分析了5种不同破坏模式的相对受压区高度。建立了各破坏模式下铝合金板加固RC梁的正截面承载力计算式,并将其与引入文献中的试验结果进行了对比分析。结果表明:试件破坏形态包括适筋破坏、端部铝合金板与结构胶剥离、端部铝合金板与梁剥离及中部铝合金板剥离4种情况;当端部设置U形铝合金箍板时,可有效抑制端部铝合金板发生剥离,使钢筋与铝合金板的材料性能得到充分发挥,试件承载力与延性明显提升;当铝合金板厚度分别为2~6 mm时,试件承载力随铝合金板厚度的增加而提高;端部设置U形铝合金箍板可有效防止端部铝合金板发生剥离,但试件仍可能会出现中部铝合金板剥离现象;当试件出现适筋破坏特征时,试件抗弯承载力的计算值与试验值比值均在1以下。本研究所提计算式具有明显的规律性和适用性,可为工程实际设计提供参考。

形状记忆合金摩擦摆隔震连续梁桥性能提升分析

为提升摩擦摆支座隔震连续梁桥的抗震性能,提出了形状记忆合金摩擦摆(SMAFP)及隔震连续梁桥多目标参数优化方法.推导了SMAFP力学模型;基于OpenSees平台分别建立了摩擦摆支座与形状记忆合金索数值模型,并通过试验验证了数值模型的准确性,进一步建立了SMAFP的数值模型.基于此,选取某三跨隔震连续梁桥,采用所提出的优化方法开展SMAFP隔震连续梁桥隔震参数优化设计,并基于最优隔震参数进一步研究了优化方法的适用性与SMAFP隔震连续梁桥的抗震性能.结果表明:采用最优参数的隔震连续梁桥的支座残余位移显著减小,2组地震动作用下的减幅分别达47.1%和44.7%,主梁峰值位移减幅分别达7.8%和11.4%,墩底剪力与墩底弯矩最大增幅分别达8.8%和9.6%.

空间滚动轴承MoS_(2)薄膜润滑分子动力学模拟

针对空间滚动轴承往复运动状态下二硫化钼薄膜润滑失效机理不明的难题,提出了采用分子动力学对薄膜润滑过程进行分析的方法。建立了单层二硫化钼薄膜摩擦原子模型,针对载荷和环境温度这2个空间滚动轴承的重要影响因素展开了二硫化钼薄膜的往复摆动模拟,得到了摩擦过程中二硫化钼薄膜的摩擦力、粘附力和磨损情况。模拟结果表明:Fe-Ni-Cr合金探针在单层二硫化钼薄膜上的摩擦为黏滑运动,载荷在20~100 nN范围内探针的摩擦过程不会对薄膜造成磨损,但在往复运动过程中润滑性能有所提高;载荷从200 nN开始探针的摩擦过程会对薄膜造成磨损,往复运动过程中摩擦系数不断提高,润滑性能下降;400 nN为单层薄膜的载荷极限,在该载荷下探针会刺穿薄膜与基底接触此时薄膜迅速磨损失去润滑作用。环境温度在1 773.15 K以下对薄膜的润滑作用影响不明显,但达到该温度后薄膜边界处开始缓慢熔化,当环境温度达到二硫化钼熔点时薄膜的熔化速度加快并失去润滑作用。从这些发现得到如下结论:二硫化钼单层薄膜在接触载荷8 GPa以下拥有优异的耐磨性和润滑性;在薄膜未破损的条件下,反复摩擦过程提升了润滑性能;二维层状结构对单层二硫化钼薄膜润滑性能有重要的影响,高温和重载都会对薄膜层状结构造成破坏。

铝合金-混凝土组合梁抗剪承载力计算方法

为了改善部分外包混凝土组合梁在使用中腐蚀生锈、钢筋混凝土劣化等问题,本文提出了铝合金-混凝土组合梁的结构形式,建立了有限元模型并进行参数分析,分析了铝合金-混凝土组合梁抗剪承载力在不同参数下的变化规律。根据改进拉压杆计算模型得到混凝土的应力传递路径,采用叠加法提出考虑铝合金梁腹板和腹部混凝土抗剪贡献的铝合金-混凝土组合梁抗剪承载力计算公式。研究结果表明:公式计算值与有限元值比值的平均值为1.018,标准差σ为0.151,表明该计算公式离散性较小,具有可行性,可以为相关研究提供理论参考。

还原熔炼法回收低品位锡中矿中锡资源

本研究采用还原熔炼法回收低品位锡中矿中锡资源,并对氧化铜为添加剂时锡的回收行为进行了探究。结果表明一定条件下,提高熔炼温度、增加焦炭添加量、延长保温时间和增加氧化铜添加量可提高锡回收率;然而温度过高时,渣中铁氧化物被还原为金属铁,并与还原态金属锡发生合金化反应生成熔点较高的Fe-Sn合金,使其在渣金分离过程中易夹带在渣中造成锡损失;熔炼过程添加氧化铜时,其可通过还原反应生成金属铜,继而与金属锡发生合金化反应生成Cu-Sn合金,热力学上降低了产物Sn的活度,促进了锡的还原回收;在焦炭添加量7%、氧化铜添加量5.8%、熔炼温度1 250℃、保温时间150 min条件下,锡回收率可达到95.24%,锡主要分布在Cu-Sn合金(分布比例90.20%)和含锡烟尘(分布比例5.04%)中。本研究实现了低品位锡中矿中锡的高效回收。