Analysis of microstructure and wear of ZnA112Pb alloy used in low‐speed bushing applications

Wear experiments on ZnAl12Pb alloy and Pb‐based Babbitt alloy (Zch PB16‐16‐2) have been carried out under identical conditions. The wear behaviour of the alloys has been investigated using scanning electron microscopy and surface profile analysis. The results show that ZnAl12Pb alloy is a good material for bushing or bearing applications, and the wear resistance of ZnAl12Pb alloy is better than that of Pb‐based Babbitt alloy.     

锌铝合金(ZA27)润滑时摩擦磨损特性研究

本文研究ZA27合金在润滑下的摩擦磨损特性。提出在油润滑下ZA27合金同材质摩擦时,磨损特点是边界润滑摩擦;其与45钢配副摩擦时,摩擦特点主要是犁削。根据磨损失重分析得出;ZA27合金在润滑工况下是一种良好的减摩材料。     

ZA27合金的性能研究与应用分析

重点介绍了ZA27合金的滑动摩擦性能和耐磨性能,并与锡青铜和"巴氏"合金的性能做了对比分析。对比结果可得,ZA27合金机械性能比锡青铜和"巴氏"合金优异、且生产成本低廉,可作为耐磨铜合金和巴氏合金的理想替代材料。     

SiCp/ZA65复合材料高温磨损性能的研究

本文研究了SiC_p/ZA65复合材料的高温耐磨性能,并与ZA27合金进行对比.结果表明,在高温干摩擦情况下,SiC_p/ZA65复合材料的耐磨性远优于ZA27合金.     

几种滑动轴承合金在油润滑条件下的磨损行为的研究

采用MPX-2000型摩擦试验机对研制的ZA30台金和ZA27、ZCuSn6Zn6Pb3、ZCuA110Fe3、ZCuSn10PI四种滑动轴承合金在46^#工业齿轮油润滑条件下的耐磨性能进行了对比试验，并在扫描电子显微镜上观察了磨损表面形貌，分析了磨损机制。结果表明：ZA30耐磨性能优于ZA27、ZCuSn10P1、ZCuSn6Zn6Pb3、ZCuA110Fe3；ZA30发生的是犁削磨损，ZA27、ZCuSn10P1主要是犁削磨损及轻微粘着磨损，ZCuA110Fe3发生的是剥落磨损，ZCuSr16Zn6Pb3发生的是粘着磨损。     

铸造及时效过程中ZA27合金调幅转变的研究

使用TEM,SEM,x-Ray衍射仪研究了ZA27合金的相变过程。结果表明：在ZA27合金中存在Spinodal转变,其组织特征为“类织物”。固溶处理后,仅在100～210℃时效时存在Spinodal转变,并沿a'面析出。铸态的Spinodal转变是由非平衡凝固引起,且短时时效不能消除其影响。     

Investigation of the tribological properties of silicon containing zinc–aluminum based journal bearings

In this study, frictional behavior of thin-walled journal bearings produced from Zn–Al–Cu–Si alloys was investigated using a purpose-built journal bearing test rig. The alloys were produced by permanent mould casting. Mechanical properties such as ultimate tensile strength, elongation, hardness and microstructure of these alloys were determined. The friction properties of the bearings produced from these alloys were also investigated. In this investigation, the effects of surface roughness and bearing pressure on the frictional properties of the journal bearings were taken into account. The results showed that friction factor decreased with increasing bearing pressure especially in the mixed and full-film lubrication zones. It was found that high surface roughness led to high friction factor. The ZnAl27Cu2Si1 and ZnAl40Cu2Si1 bearings showed full Stribeck curve tendency while ZnAl27Cu2Si2 bearing did not exhibit the typical diagram having no full-film lubrication zone at the pressure of 0.7 and 1.1 MPa.     

Sliding wear of cast zinc-based alloy bearings under static and dynamic loading conditions

The lubricated wear behaviour of cast journal bearings, produced from a series of zinc-based alloys and SAE 660 bronze as a reference material, was investigated under both static and dynamic loading conditions using a bearing test rig. All of the zinc-based alloys had higher wear resistance than the SAE 660 bronze. Among the zinc-based alloys, the wear resistance of the monotectoid-based alloys was superior to those based on near-eutectoid composition, and the best wear performance under both static and dynamic loading conditions was obtained with ZnAl40Cu2Si1 alloy. Copper content affected the wear resistance of monotectoid zinc-based alloys. Under dynamic loading conditions, it increased with increasing copper content up to 2%, but declined thereafter. Tensile properties and hardness of the monotectoid alloys were also affected by their copper content. Loading conditions had a strong influence on the wear rate. Under static loading conditions, as-cast zinc-based alloys showed higher wear resistance than the equivalent heat-treated alloys, but this behaviour was reversed for dynamic loading. Possible reasons for this are briefly discussed.     

The influence of alumina particle dispersion and test parameters on dry sliding wear behaviour of zinc-based alloy

The present investigation deals with dry sliding wear characteristics of a zinc-based alloy (ZA 37) with and without Al₂O₃ particle dispersion over a range of sliding speeds and applied pressures. The matrix alloy has been examined under identical test conditions in order to examine the role played by the second phase alumina particles on wear behaviour. The observed wear behaviour of the samples has been explained in terms of specific characteristics like cracking tendency, lubricating, load bearing and deformability characteristics, and thermal stability of various microconstituents. The nature of predominance of one set of parameters (causing higher wear rate) over the other (producing a reverse effect) was thought to actually control the wear behaviour. Examinations of the characteristic of wear surfaces and subsurface regions also enabled to understand the operating wear mechanism and to substantiate the wear behaviour.At low sliding speed, significantly lower wear rate of the matrix alloy over that of the composite was noticed. This has been attributed to increased microcracking tendency of the composite than the matrix alloy. Reduced wear rate and higher seizure pressure experienced by the composite over that of the matrix alloy at the higher sliding speeds could be explained to be due to enhanced compatibility of matrix alloy with dispersoid phase and greater thermal stability of the composite in view of the presence of the dispersoid. The maximum temperature rise due to frictional heating has been observed to be low in the case of matrix alloy than composite at low speed while the trend reversed at higher speeds. In general, the wear rate and temperature increased with applied pressure and speed. Seizure pressure reduced with increasing speed while the seizure resistance (pressure) of the matrix alloy was more adversely affected by speed than that of the composite.     

曳引机用蜗轮的制造研究与实践

分析了曳引机用蜗轮副的选材和蜗轮制坯采用新型ZA27合金的铸造方法,介绍了非对偶法蜗轮加工理论,分析了非对偶法蜗轮滚刀的设计方法及在生产实际中的应用.     

新型耐磨锌合金的轴承台架试验研究

通过在ZA27合金中添加Mn或Si等合金元素,制备出两种新型耐磨锌合金。相分析结果表明,它们的组织中含有较多弥散分布的硬质相,如含锰的金属间化合物或初生硅晶粒,这些硬质相的硬度远远高于ZA27合金中硬质点相ε。通过抗压性能测试和轴承台架试验,发现与两种传统的轴承合金ZA27和磷锡青铜ZCuSn10P1相比,新型耐磨锌合金的抗压性能良好、摩擦系数较低、滑动过程平稳、表面温升较低、耐磨性较好。新型锌合金优异的摩擦磨损性能与其耐磨微观组织有密切的关系。     

硅和锡对ZA27锌基合金耐腐蚀性能的影响

在35g／LNaCl水溶液中,用电化学测量系统测定了硅加入量分别为0．11％,0．19％,0．30％和锡加入量分别为0．10％,0．15％,0．21％,0．26％的ZA27锌基合金的塔菲尔曲线、腐蚀电位、线性极化电阻和腐蚀电流密度等电化学参数,在扫描电镜下观察了腐蚀后的形貌,并与二元ZA27合金进行了比较。结果表明：硅和锡的加入使试验合金的腐蚀电位朝负向移动,腐蚀电流密度增加,均降低了ZA27高铝锌基合金的耐腐蚀性能,其中锡的影响较大．     

Effect of Copper Content on the Mechanical and Tribological Properties of ZnAl27-Based Alloys

One binary ZnAl27- and five ZnAl27-based ternary alloys containing 1–5% Cu were produced by permanent mould casting. Their friction and wear properties were examined using a block-on-ring test machine after determining their hardness and tensile strength. It was observed that the hardness and tensile strength of the ZnAl27-based ternary alloys increased with increasing copper content up to 2% due to solid-solution hardening, above which their tensile strength decreased, while hardness continued to increase. This is attributed to the formation of copper-rich and T phases, which reduce the solid-solution hardening of the alloys. It was found that the wear volume loss of the ZnAl27-based alloys decreased with increasing copper content up to 2% but showed a small increase above this level. Therefore, it was concluded that the wear resistance of ZnAl27-based alloys containing 1 to 5% Cu correlates well with their tensile strength. In addition, smearing and scratches were found to be the main features of the wear surfaces of the ZnAl27-based alloys under static loading and lubricated sliding conditions.     

Mechanical properties and lubricated wear of Zn-25Al-based alloys

Seven alloys based on Zn-25Al were produced as binary alloys or with silicon or copper ternary additions. Tensile properties, hardness and dimensional stability were studied in the as-cast state and as a function of aging.The lubricated wear behaviour was studied using a special pin-on-disc method and compared with that of SAE 660 bronze and SAE 73 brass.The addition of copper was found to be more effective than silicon in improving the mechanical properties of Zn-A1 alloys but silicon gave greatly improved wear resistance and dimensional stability. The wear resistance of Zn-Al-Si alloys was found to be superior to that of all the other materials tested.A heat treatment performed to simulate long term aging reduced the hardness and tensile strength of all the zinc-based alloys by about the same amount but improved ductility. The wear resistance was reduced by an increase in the break-in wear but was only significant for the alloy containing copper.It is concluded that Zn-Al-Si alloys have good bearing properties but may not have adequate strength after prolonged aging. An alloy with a composition close to that of ZA27, but with reduced copper and added silicon, may produce an improved combination of mechanical strength and wear resistance with a slight reduction in density.     

Large deformation compression–torsion behaviour of a titanium alloy and its modelling

A range of sequential and compound compression-torsion tests has been carried out on titanium alloy IMI834 at 1000°C and nominal true strain rate 5 × 10⁻³ s⁻¹, typical of forging conditions. The tests were used to investigate initial and subsequent yield and flow behaviour, the nature of the material hardening and the effect of flow softening on subsequent deformation. In addition, a material model with isotropic or directional hardening has been used to predict the material behaviour.The results show that the material behaviour at large strains is reasonably isotropic, although a directional hardening model provides slightly better quantitative agreement with the experimental results. Large pre-strains (0.4), either axial or torsional, are found not to change significantly subsequent material behaviour. A stress state dependence of flow softening is observed to exist.The material model presented is shown to give good quantitative agreement of predicted and experimental results.     

Influence of T4 Heat Treatment on Tribological Behavior of Za27 Alloy Under Lubricated Sliding Condition

The effects of heat treatment on the microstructure, hardness, tensile properties, and tribological behavior of ZA27 alloy were examined. The alloys were prepared by conventional melting and casting route. The heat treatment of samples included the heating up to 370 °C for 3 or 5 h, quenching in water, and natural aging. Lubricated sliding wear test were conducted on as-cast and heat-treated ZA27 samples using block-on-disc machine. The friction and wear behavior of alloys were tested in contact with steel discs using combinations of three levels of load (10, 30, and 50 N) and three levels of linear sliding speeds (0.26, 0.50, and 1.00 m/s). To determine the wear mechanisms, the worn surfaces of the samples were examined by scanning electron microscopy (SEM). The heat treatment resulted in reduction in the hardness and tensile strength but increase in elongation. The heat-treated alloy samples attained improved tribological behavior over the as-cast ones, under all combinations of sliding speeds and contact loads. The rate of improvement increased with duration of solutionizing process before quenching in water. Obtained tribological results were related to the effects of heat treatment on microstructure changes of alloy.     

Fretting wear behaviour of hypereutectic P/M Al–Si in oil environment

The fretting wear behaviour of forged hypereutectic P/M Al–Si in contact with hardened steel and Cu–Sn–Pb bearing material is investigated. Fretting tests are performed with a view to the movement in the contact between the small end of the connecting rod and the piston pin in a car engine. Therefore, the tests are carried out under engine oil lubrication at temperatures up to 150°C. The behaviour of the Al alloy is compared to that of steel, the current connecting rod material. Some tests under non-lubricated conditions are also performed. The correlation between the friction coefficient, the wear volume and the microscopic wear mechanisms is discussed. After the running-in wear, a stable wear condition is reached for the Al–Si/steel contact.     

Erosive wear by silica sand on AISI H13 and 4140 steels

The erosive wear behaviour of AISI H13 tool steel and AISI 4140 steel has been investigated in this work using a sand blast-type rig. Samples of six different hardness levels (from annealed to 595 HV) were produced and subsequently tested using silica sand as the erodent material at impact angles ranging from 10° to 90°, air drag pressures of 0.689 and 1.38 bar (10 and 20 psi respectively), impact speeds ranging from 70 to 107 m s⁻¹ and various particle sizes. Results of erosion versus impact angle at different hardness levels showed three distinctive wear regions: (i) for impact angles of 10° and 20°, the amount of wear was higher at lower hardness values; (ii) for impact angles of 30° and 40° no significant changes were found in the amount of wear despite the increase in hardness; (iii) for impact angles of 60°, 75° and 90° the amount of wear was higher for higher hardness levels in the eroded material. Single curves showed typical ductile behaviour of these alloys, a transition towards brittle behaviour for the hardest specimens was also observed due to the formation of adiabatic shear bands. SEM analysis was conducted to identify the erosion mechanisms for each type of behaviour.     

Bio‐lubricant flow behaviour in mini‐channels

One of the most common causes of failures in total joint replacements is the generation of wear particles within the joint. This contributes to bone lost and aseptic loosening of the implant, eventually requiring its replacement. Many studies have been carried out to improve the wear characteristics of bearing surfaces in total joint replacement. From the lubrication point of view, the friction behaviour of surfaces and rheology of the joint lubricant (synovial fluid) have been extensively studied. However, little attention has been paid to the interaction between the lubricant and the bearing surfaces. The aim of this study is to develop a methodology for studying the behaviour of bio‐based lubricant in mini‐channels. For this purpose, micro‐particle image velocimetry was used in order to characterise the lubricant behaviour. Channels made of relevant materials such as ultra‐high molecular weight polyethylene, cobalt–chromium–molybdenum alloy and titanium–aluminium–vanadium alloy with 1 and 1.5 mm width, 45 mm length and 2 mm depth were experimentally investigated. Results suggested that the used polymeric solution interaction with solid surfaces is very sensitive to the polymer concentration in the lubricant. Moreover, it was observed that there exist differences between water (Newtonian reference fluid) and the polymeric solution behaviour even at very simple movements; although usually, the properties of this lubricant at high shear rates are estimated by water properties. Copyright © 2015 John Wiley & Sons, Ltd.     

Influence of grain orientations on the initiation of fatigue damage in an Al–Li alloy

The variation in microstructure and texture in a rectangular bar extruded from a billet of spray-cast 8090 Al–Li alloy has been examined. The fine grain size of the as sprayed billet and the moderate extrusion ratio (≈ 25 : 1) were seen to cause geometric dynamic recrystallization (GDR) in regions of higher strain towards the edge of the bar. The grain morphology varied from the expected elongated grains at the centre of the bar to equiaxed grains where GDR occurred at the bar edges. A <111> + <100> double fibre texture, significantly distorted towards rolling components and varying through the bar thickness, was found using electron backscatter diffraction. Fatigue resulted in a high density of short secondary cracks, many of which had arrested at grain boundaries. The cracks preferentially nucleated in grains from the <100> fibre texture corresponding to high Schmid factors.