Influence of Aluminum on the Mechanical and Tribotechnical Properties of Sintered Copper-Based Friction Material

The principal physicomechanical and tribotechnical characteristics of friction materials based on tin bronze and aluminum-tin bronze have been studied over a wide range of velocities and friction loads. Aluminum-tin bronze which has slightly higher strength characteristics, is significantly harder than a similar tin bronze. This in turn affects the friction characteristics of the material, increasing the friction coefficient and wear resistance.     

Creep of tin, Sb-solution-strengthened tin, and SbSn-precipitate-strengthened tin

The creep properties of tin-antimony alloys were studied up to the peritectic composition. For tin at temperatures below approximately 150 °C, creep is dominated by pipe diffusion-controlled climb with a stress exponent of 8 and activation energy of 70 kJ/mol. At high stresses, small amounts of impurities cause a transition to a less stress sensitive, most likely solute drag-controlled mechanism. Antimony atoms in solution have only a minor effect on these creep properties. Alloys with higher compositions of antimony contain whiskerlike SbSn precipitates. These alloys exhibit a discontinuous transition in stress exponent and activation energy at an intermediate stress. The creep behavior of these alloys is described fairly well by a composite theory in which the power law stress is divided by a strengthening coefficient, and the strengthening coefficient is related to the precipitate volume fraction and the aspect ratio. Using a friction stress and a strengthening coefficient simultaneously, the behavior of these alloys can be described entirely in terms of tin creep constants. Aging at 100 °C has little effect on the creep properties of the precipitation-strengthened alloys. It is expected that solder alloys strengthened by these precipitates would maintain a significant fraction of their creep strength for significant periods at temperatures below 100 °C.     

Effects of Copper Powder Bearing Material Composition on Working Characteristics

Effects have been established for phosphorus and lead on the working characteristics of tinned bronze with high-speed operation (up to 20000 rpm or up to 2 m/sec) at low pressures (up to 2.0 MPa). It has been found that Cu - Sn - Pb - CP powder bearing material, where CP is a copper-phosphorus alloy, under such conditions has a lower coefficient of friction than does tinned bronze and a much higher wear resistance, while sliding bearings based on it have high working life. A microheterogeneous structure is formed in this material: an α-solid solution of tin in copper, along the boundaries of which there is uniformly distributed a strengthening phase (network of copper phosphide Cu₃P with inclusions of the phosphide eutectic Cu₃P + Cu₃Sn + (Cu - Sn), and there are lead inclusions at the grain boundaries intersections. This material has very good tribotechnical characteristics at high rotation speeds and low pressures and also low coefficient of friction, low wear, and consequently long working life of bearings made of it.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 120–126, March–April, 2005.     

Production and properties of metal-PTFE antifriction materials from atomized bronze powders

Conclusions An investigation into the sinterability of loosely poured atomized bronze powders has established that the porosity of resultant sintered bronze skeletons depends on the particle size and shape. The shape of the bronze powder particles has some effect on the antifriction characteristics of a metal -PTFE material, but its coefficient of friction and wear resistance are affected more strongly by the composition of a solid lubricant introduced into the pores of its sintered skeleton. Using a nonspherical rather than spherical bronze powder gives a bronze saving of 15–20% without affecting the good antifriction properties of metal-PTFE materials, by increasing the porosity of their skeletons. Replacing molybdenum disulfide with graphite substantially increases the wear resistance of two-layer metal-PTFE materials and markedly decreases their cost, since the price of molybdenum disulfide is more than 20 times that of graphite.Translated from Poroshkovaya Metallurgiya, No. 9(273), pp. 30–34, September, 1985.     

皖南地区的早期矿冶遗址以及三种合金技术

对皖南地区的早期矿冶遗址进行综合考察研究,发现存在着配制锡青铜、砷青铜、锑青铜的3种合金技术。青铜冶炼流程为两步法,所用铜料、砷料、锑料应来自当地,锡料推测来自长江中游的赣北且主要以锡砂形式添加。研究还发现,以皖南为代表的长江下游是中国早期又一处重要的砷青铜冶金区,其生产流行的资源背景应与该地区缺乏锡矿有关。研究进一步预示长江流域存在着相当规模且独具特色的早期青铜冶金业,而与黄河流域的中原地区有明显区别。     

The Effect of Thermomechanical Processing on the Tensile, Fatigue, and Creep Behavior of Magnesium Alloy AM60

Tensile, fatigue, fracture toughness, and creep experiments were performed on a commercially available magnesium-aluminum alloy (AM60) after three processing treatments: (1) as-THIXOMOLDED (as-molded), (2) THIXOMOLDED then thermomechanically processed (TTMP), and (3) THIXOMOLDED then TTMP then annealed (annealed). The TTMP procedure resulted in a significantly reduced grain size and a tensile yield strength greater than twice that of the as-molded material without a debit in elongation to failure (ε _f ). The as-molded material exhibited the lowest strength, while the annealed material exhibited an intermediate strength but the highest ε _f (>1 pct). The TTMP and annealed materials exhibited fracture toughness values almost twice that of the as-molded material. The as-molded material exhibited the lowest fatigue threshold values and the lowest fatigue resistance. The annealed material exhibited the greatest fatigue resistance, and this was suggested to be related to its balance of tensile strength and ductility. The fatigue lives of each material were similar at both room temperature (RT) and 423 K (150 °C). The tensile-creep behavior was evaluated for applied stresses ranging between 20 and 75 MPa and temperatures between 373 and 473 K (100 and 200 °C). During both the fatigue and creep experiments, cracking preferentially occurred at grain boundaries. Overall, the results indicate that thermomechanical processing of AM60 dramatically improves the tensile, fracture toughness, and fatigue behavior, making this alloy attractive for structural applications. The reduced creep resistance after thermomechanical processing offers an opportunity for further research and development.     

Wear Behavior of the Lead-Free Tin Bronze Matrix Composite Reinforced by Carbon Nanotubes

Copper-coated carbon nanotubes were prepared by the electroless plating route. The structure and component of copper/carbon tubes were characterized using a transmission electron microscope and energy dispersive spectrometer. The results show that the surface of the carbon tubes was covered by the copper particles. Copper/carbon tubes were used as the substitute of part of tin and all of lead in the tin bronze matrix, and the tribological properties of carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composites were studied. The effects of the carbon nanotube volume fraction and sliding distance in unlubricated ball-on-disc wear test were investigated. The 3 vol pct carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composite shows the Vickers hardness of 126.9, which is approximately 1.6 times higher than that of Cu-6 wt pct Sn-6 wt pct Zn-3 wt pct Pb tin bronze. The wear rate and average friction coefficients of 3 vol pct carbon nanotube-reinforced Cu-4 wt pct Sn-6 wt pct Zn composite were lower than those of the Cu-6 wt pct Sn-6 wt pct Zn-3 wt pct Pb tin bronze, respectively.     

Tribological Characteristics of Materials Based on Bronze for Small Friction Assemblies

The effect of the fineness of atomized nonspherical bronze powder and compaction pressure on the porosity and pore size of sintered materials is studied. The optimum sintering temperature for achieving the maximum strength and porosity of bronze carcasses is determined. The effect of bronze original porosity and powder particle size on the wear resistance and friction coefficient of sintered carcasses impregnated with polymer and oil under dry friction conditions and a self-lubricating regime is established.     

Megalithic and Continuing Peninsular High-Tin Binary Bronzes: Possible Roots in Harappan Binary Bronze Usage?

This paper attempts to trace the development of an unusual and skilled class of alloys, of binary high-tin bronze (i.e. alloys of only copper with a higher percentage of tin), which are found from surprisingly early contexts from Indian antiquity. In particular, the deliberate use was made of binary beta bronze with around 22–24 % tin, specifically exploiting the properties of higher hot-forgability of bronze of this composition due to the formation of the high temperature beta intermetallic compound phase of 22.9 % tin. Quenching resulted in the retention of the beta phase, yielding a musical alloy with golden lustre and improved tensile strength as compared to the as-cast state. Examples of hot forged and quenched high-tin beta bronzes studied by the author from the South Indian Iron Age and megalithic cultures from Tamil Nadu and Maharashtra and Gandharan Grave Culture of Taxila are summarised here ranking amongst the earliest and most finely wrought such finds. There are technological and morphological similarities to surviving high-tin bronze crafts practices documented by the author in Kerala since 1990. Since the 1990’s she has also documented the making of high-tin delta bronze mirrors at Aranmula with a composition closer to the pure delta phase of 32.6 % tin, which instead exploited the specular properties this alloy while managing its brittleness. Although it is difficult to speculate about origins, a long standing practice of using binary tin–bronzes (i.e. only copper–tin alloys) can be detected going back to Harappan bronzes which also seem to be predominantly binary bronzes with not much lead added to them. Though most of these seem to be low-tin bronze, the presence of a couple with higher tin of about 20 % is also notable in terms of the above discussion.     

High temperature embrittlement of NI and Ni-Cr alloys by trace elements

The effects of Sb, Sn, and Zr additions on the creep properties of Ni and Ni + 20 pct Cr are reported. Antimony and tin additions (~1 wt pct) induce extensive grain boundary cavitation in nickel, while smaller antimony additions had little effect on Ni + 20 pct Cr. Addition of 0.11 pct Zr to Ni + 20 pct Cr greatly inhibited grain boundary cavitation and reduced its Coble creep rate. Auger electron spectroscopy of cavitated specimens provided direct evidence of impurity segregation to cavity surfaces. Residual sulfur segregated most strongly, and was observed on cavity surfaces in all cavitated specimens. Tin segregated somewhat less intensely than sulfur, and antimony segregated only slightly. Segregation of antimony and sulfur to uncavitated portions of Ni + 1 pct Sb grain boundaries was also observed. These results are discussed in terms of segregation effects on energetic and transport properties of the grain boundaries and cavity surfaces. This paper is based on a presentation made at the symposium “The Role of Trace Elements and Interfaces in Creep Failure” held at the annual meeting of The Metallurgical Society of AIME, Dallas, Texas, February 14-18, 1982, under the sponsorship of The Mechanical Metallurgy Committee of TMS-AIME.     

Sintered ferrous antifriction materials for arduous operating conditions

Summary The main methods by which the load carrying capacity of ferrous antifriction materials may be raised are to increase the strength of their metallic matrix by suitable alloying and to decrease their coefficient of friction by the addition of various sulfides. Researches in this field have led to the formulation of a new class of sulfidized ferrous materials. The investigation has shown that, if the load carrying capacity of a material is to be increased, the latter must contain structurally free graphite and sulfides, which secure the formation of stable working films with a low coefficient of friction. The best antifriction properties for the type of material investigated are ensured by a pearlitic-ferritic structure with a pearlite content of not more than 50%.The highest antifriction properties are exhibited by iron-graphite base materials containing 4% zinc sulfide with additions of 1% tin and 1% elemental sulfur.Translated from Poroshkovaya Metallurgiya, No. 8(56), pp. 39–45, August, 1967.     

湖南益阳商代青铜角形器的科学分析与相关问题探讨

益阳谢林港出土了一件商代兽面纹青铜角形器,是上古铜器中少见的一类器物。由于考古信息缺失,利用金相显微镜、扫描电镜能谱仪和固体表面热电离质谱仪对该角形器进行科学分析。结果表明,器物为铸造成型,合金材质为锡含量16.54%的高锡含量青铜,铅同位素组成为高放射成因铅,其合金和铅同位素特征与中原殷墟二期铜器相同,结合器物纹饰,益阳青铜角形器应为殷墟二期的器物。殷墟二期铜器普遍具有高锡现象,表明商代晚期铸铜工匠对铜锡合金机械性能的认识达到了新的高度。商代晚期铜锡合金青铜器的大规模铸造是中国古代第一个用锡高峰,反映了古代锡金属开采和冶炼技术质的提升,在中国冶金史上具有里程碑意义。     

Structural Wear-Resistant Sintered Materials Based on Titanium

A principle is proposed for increasing the wear resistance of structural titanium materials by addition (together with a moderate number of hard inclusions) of alloying elements which, without decreasing the strength and ductility of titanium, increase the wear resistance of the material thanks to the formation of oxide films during friction that prevent seizing of the contacting surfaces. Requirements for the hard inclusions and alloying additions were defined, the basic of which is a high affinity of the alloying elements for oxygen. Grades of wear-resistant structural titanium materials were created and recommended for use in the production of components operating in friction units at room temperature (IT20, IT15V) and at 250-550°C (IT16M). The mechanical properties and operating conditions (sliding rate, pressure, temperature, counterbody material, atmosphere) of the sintered titanium materials were investigated.     

Effect of additions of indium,tin, bismuth,and tungsten oxides on the properties of a silver-cadmium oxide composite

Conclusions The addition of 5% of bismuth oxide to an Ag-10% CdO powder composite enhances the erosion resistance of contacts made from it. Similar additions of tungsten and indium oxides adversely affect, and one of tin oxide has but little effect on, the erosion resistance of Ag-15% CdO composite contacts. Bismuth oxide and, to an even larger extent, indium oxide improve the resistance to welding of these contacts. The effect of the oxides on the structure and resistance to erosion and welding of the contacts is determined by their ability to react with the components of the matrix and by the properties of the reaction products.Translated from Poroshkovaya Metallurgiya, No. 11(287), pp. 20–26, November, 1986.     

High-temperature friction of alloys of the TiNx-TiB2 system

Conclusions It has been established that the highest transverse rupture strength and wear resistance combined with the lowest coefficient of friction are shown by alloys of eutectic composition. In alloys of the TiN_0·9-TiB₂ system higher ductility during friction is exhibited by the boride phase, whose substructure experiences greater changes compared with the nitride phase. The greatest deformation during friction characterizes the phases in the TiN_0·73-TiB₂ alloy. The strengthening and strength loss processes at temperatures of 20–400°C are determined by the strength loss processes occurring in the boride phase, and those above 400°C, by the strengthening and strength loss processes taking place in the nitride phase.Translated from Poroshkovaya Metallurgiya, No. 2(242), pp. 70–76, February, 1983.     

弹性连接器组件研究现状及进展

弹性连接器常用于电流和信号的传输，在现代电子通讯领域被广泛应用。其制备过程中的冲压工艺，受到包括冲压方向、冲压角度、冲压宽度、最小相对弯曲半径等因素影响。其制备材料的导电率、摩擦系数、耐腐蚀性将影响弹性连接器的接触阻抗，同时材料本身的弹性模量、强度、抗热应力松弛率、摩擦系数等，将影响弹性组件的可靠性，而接触阻抗和可靠性将直接影响弹性连接器通讯电讯号的传输。本文从选材的角度，针对电力传输用连接器的电导率、弹性模量、强度、摩擦磨损性能、冲压性能和抗热应力松弛性能，信号传输用连接器的弹性模量、强度、冲压性能、表面电导率，以及高温下长周期服役用连接器的抗热应力松弛性能和耐腐蚀性，反复插拔用连接器的接触组件表层的耐摩擦磨损性能等分别进行了综述，同时从加工的角度提出弹性连接器需要结合设计考虑不同冲压方向、冲压角度、冲压厚度、冲压宽度下的最小相对弯曲半径。     

Effects of temperature on the friction characteristics of composite materials based on W,W2B5, and WC

Summary A study was made, under atmospheric conditions, of the dry friction of W, W₂B₅, and WC with various boron-nitride additions, subjected to bulk heating. The effects of heating temperature on the coefficients of friction and wear of these materials were determined.Translated from Poroshkovaya Metallurgiya, No. 10 (70), pp. 80–84, October, 1968.The authors wish to express their gratitude to V. N. Rudenko for conducting strength measurments on the materials investigated at elevated temperatures (up to 773°k).     

含锑软钎料钎焊黄铜组织与性能的研究

为判断含锑钎料钎焊黄铜是否可行 ,研究了锡铅锑钎料钎焊H6 2黄铜时锑与锌的作用 ,并对其接头的组织与性能进行了深入分析。研究结果表明锡铅锑钎料钎焊黄铜的接头组织中未发现锌锑化合物相 ,含锑量0 2 2 %～ 0 .8% (质量分数 )的锡铅锑钎料钎焊黄铜未引起接头性能下降 ,认为可以钎焊黄铜。     

微波消解-电感耦合等离子体原子发射光谱法测定甲基磺酸盐(MSA)电镀锡泥中铜镍铅锑铋

甲基磺酸盐(MSA)体系电镀锡板在生产过程中,电镀液中的锡发生氧化会在阳极形成锡泥,这种固废产物中的重金属元素如果处理不当,将危害环境,因此准确测定电镀锡泥中金属元素的含量有利于指导其后续处理。实验采用硝酸-盐酸-氢氟酸并采用微波消解法对样品进行消解,可有效除去锡泥中有机物且不会造成待测元素的损失;采用基体匹配法消除基体效应的影响,选择Cu 324.754 nm、Ni 231.604 nm、Pb 220.353 nm、Sb 206.833 nm、Bi 190.241 nm为分析谱线,建立了电感耦合等离子体原子发射光谱法(ICP-AES)测定MSA电镀锡泥中铜、镍、铅、锑、铋的方法。结果表明:在仪器最佳工作条件下,各元素校准曲线的线性相关系数均大于0.999 5,各元素检出限为0.000 2%~0.000 6%。按照实验方法测定MSA电镀锡泥中铜、镍、铅、锑、铋,结果的相对标准偏差(RSD,n=8)均小于3%,加标回收率为97%~104%。按照实验方法测定MSA电镀锡泥样品中铜、镍、铅、锑、铋,结果与火焰原子吸收光谱法测定铜、镍、铅,硫酸铈滴定法测定锑,EDTA滴定法测定铋的对比结果一致性较好。     

电感耦合等离子体质谱法测定锰铁中痕量铅锡锑

建立了电感耦合等离子体质谱法（ICP-MS）同时测定锰铁中痕量铅、锡和锑的分析方法。采用HCl、HNO₃、HF和HClO₄溶解样品, 过氧化氢还原氧化锰, 内标法和基体匹配来校正基体效应, 通过优化质谱仪测量参数, 选择²⁰⁸Pb、¹¹⁸Sn和¹²¹Sb作为待测元素同位素, 测定了锰铁中铅、锡、锑含量。研究结果表明：铅、锡、锑校准曲线的线性相关系数在0.999以上, 检出限(质量分数)分别为0.0005%、0.00008%、0.00011%, 样品测定结果与ICP-AES法相符, 相对标准偏差（n=10）分别为3.5%(铅)、7.2%(锡)、5.9%(锑)。该方法分析周期短, 精密度和准确度能满足测量要求。