铸造锌铝合金-ZA新系列

本文将通过与现有的铸造锌合金及其它合金的比较,重点介绍ZA系铸造锌合金的化学成份,机械性能、铸造性能以及其它特殊性能;同时阐述ZA系合金的熔炼方法;最后扼要介绍ZA系合金的应用情况。     

硅合金化耐磨锌合金

在高强度铸造锌合金中添加硅作为合金组织中的硬质点,可获得新型耐磨铸造锌合金。该合金的减摩、耐磨性能及承载能力均优于锡青铜和不加硅的高强度铸造锌合金。本文阐述了此合金的成分、组织与性能、摩擦与磨损特性、轴承的设计与使用参数、熔铸工艺特点以及用锡青铜的实际使用效果。     

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。     

ZMJ高强度耐磨锌合金

华南理工大学研制的一种新型高强度耐磨锌合金(代号ZMJ)已通过技术、产品鉴定.该材料属国内首创,处于国际领先水平.它具有优良的摩擦磨损性能和综合机械性能.用该合金生产的试样与ZCuSn10P1铜试样相比,耐磨性高7.6倍以上,减摩性高28.1%,承载能力高9.67倍;与美国ZA—27锌合金试样相比,耐磨性高5～43.2倍,承载能力高3倍,最高允许工作温度由150℃提高到170℃,最大容许滑动速度可达8m/s.与GB1176     

新的铸造锌合金

加拿大Noranda Mines公司研制了ZA8, ZA12和ZA27锌基铸造合金。这类合金成本低,铸造性能好,机械性能和机加工性能均理想,应用范围广,既可砂型铸造,也可压铸。有时其性能可相当于铝合金。这三种合金是在ILZRO-12合金(含铝12％、铜0 .75％和镁0.015％)基础上研制成功的。室温下这类铸造合金的正常机械和物理性能如表1。由表可知这些新型铸造合金是抗拉强度高、布氏硬度大及熔点低。表2为这些合金的标准性能与铜、LM25M铝合金及灰口铁的比较。ZA8与ZA12、ZA27比较,冷凝温度范围最小,     

含钇稀土的新型ZA-27锌合金

在ＺＡ－２７锌合金中添加适量钇稀土,能使其抗拉强度、延伸率、硬度有所提高,滑动磨擦系数降低、磨擦量减少,耐磨性能提高。从微现组织分析,添加适量的钇稀土后,能使ＺＡ－２７合金的显微缩松消除,并使合金的花瓣形ａ－技晶组织转变为等轴组织,致密度提高,同时合金也析出耐磨的钇锌硬质点相,镶嵌在软基体上,在摩擦磨损过程中起着支撑作用。提高合全的减摩性和耐磨性,使合金的磨擦系数下降,耐磨性能提高。     

喷射沉积ZA35-3.5%Mn合金的力学和摩擦磨损性能

在ZA35合金基础上添加适量的合金元素锰,采用喷射沉积 热挤压的成形方法获得试验材料,对试验材料的力学性能和摩擦磨损性能进行了测试,用扫描电镜观察了其组织和磨损形貌,用X射线衍射仪测定了物相.结果表明:喷射沉积ZA35-3.5%Mn合金与金属型铸造相同成分合金相比,前者组织均匀,晶粒细小,抗拉强度明显提高,达到484.2 MPa;喷射沉积ZA35-3.5%Mn合金中的合金元素锰形成了硬质相作为承载相,使其耐磨损性能提高.     

GW50钢结硬质合金模具渗硼强化新工艺

钢结硬质合金国外被誉为“80年代新型工程材料”之一,应用于飞机、火箭发动机、宇航飞船上的耐热、耐磨、耐腐蚀零件和工模具制造,我国近年来有了较快发展,主要应用于冷作模具制造。钢结硬质合金以高熔点WC(或TiC)为硬质相,以合金工具钢作为粘结剂,将二者混合,采用粉末冶金真空烧结而成。硬质相颗粒均匀分布于钢基体上。性能介于硬质合金与合金工具钢之间,综合了二者的性能长处。它具有钢材“四性”特征:即可加工性、可锻性、可焊性和可热处理,又有硬质     

化学成分对锌铝合金动态断裂性能的影响

用Hopkinson杆加载系统在不同加载速率下,研究了ZA8、ZA27和ZA35三种锌铝合金的动态断裂性能随化学成分的变化趋势;并用扫描电镜对试样的断口形貌进行了观察。结果表明:在加载速率一定的情况下,随着合金中铝含量的增加,合金中面心α相含量逐渐增加,断口形貌由解理状向韧窝状转变,其动态断裂能和加载速率敏感性逐渐增大;而随着加载速率逐渐增大,只有ZA8合金的断口形貌不发生变化,ZA27、ZA35合金断口形貌由韧窝状向准解理状转变,使两者的动态断裂能随加载速率的增大而减小,并导致其加载速率敏感性逐渐降低。     

固溶时效稀土变质ZA27合金阻尼性能及机理

对铸造稀土变质ZA27合金进行固溶处理，并进行长时间自然时效。测量了合金的阻尼性能，用透射电镜对合金固溶时效后的微观结构进行了研究。结果表明：固溶时效后合金的阻尼性能有较大提高。合金高阻尼性的微观机理主要是α相和η相两相界面发生粘滞性滑动以及α相发生局部微塑性变形，消耗了振动能量。合金在固溶时效后组织得到改善和细化，增大了界面面积，从而提高了阻尼性能。     

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。     

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.     

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.     

Reciprocating Sliding Wear Performance of Hard Coating on Modified Titanium Alloy Surfaces

The high strength, low weight, and outstanding corrosion resistance properties possessed by titanium alloys have led to a wide range of successful applications in aerospace, automotive, and chemical industries and in power generation. Titanium alloys are characterized by poor wear resistance properties and their utilization has been excessive in nontribological applications. Surface texturing is a well-known and effective means of surface modification to improve the tribological properties of sliding surfaces. In the present work, modification of titanium alloy surfaces (Ti6Al4V) was done by lapping and laser surface texturing. The wear-resistant coating, AlCrN, was applied over the modified titanium alloy surfaces, with and without a chromium interlayer. Linear reciprocating sliding wear tests were performed with ball-on-flat contact geometry to evaluate the tribological performance of the coated alloy. The tests were performed under different normal loads for a period of 105 cycles at a frequency of 5 Hz. The friction force between the contact pair and displacement of the ball were simultaneously observed using a force transducer and laser displacement sensor. Optical microscopy was used to quantify the wear volume by measuring the wear scar diameter on both the specimen and the counterbody. Scanning electron microscopy (SEM) was employed to study the morphology of the wear scar. The characteristic behavior of the AlCrN coating such as bonding strength, wear volume, wear rate, and coefficient of friction with the chromium interlayer was evaluated and compared with the coating directly applied over the substrate. The coating on the textured surface, with the chromium interlayer showed better tribological performance.     

Sliding friction and wear of magnesium alloy AZ91D produced by two different methods

Alloy AZ91D is a leading magnesium alloy used for structural applications. It contains aluminum and zinc as principal alloying elements. This alloy is normally die-cast, but recent developments in semi-solid injection molding (Thixomolding^®), which offers certain processing advantages, produces a slightly different microstructure than die-casting, and it was of interest to determine whether the two processing routes would measurably affect the friction and wear of AZ91D. The present work involved ambient air, room temperature testing of die-cast (DC) and Thixomolded^® (ThM) AZ91D, in both unidirectional and reciprocating sliding motion, using stainless steel type 440C as the counterface. After running-in, the average sliding friction coefficients in both types of test fell into the range of 0.29–0.35, irrespective of processing method. The formation of a built-up edge raised the friction slightly in unidirectional tests compared with reciprocating tests. The average wear rate of the ThM alloys in reciprocating sliding was approximately 25% lower than that for DC alloys. However, the wear rates of the magnesium specimens in unidirectional sliding were comparable for DC and ThM materials. Owing to the transfer of magnesium, there was no measurable wear on the stainless steel 440C balls. The wear mechanism during sliding involves the formation of thin, narrow shards along the edges of wear grooves which break off to produce loose particles.     

Influence of Test Conditions on the Lubricated Friction and Wear Behaviour of Al–25Zn–3Cu Alloy

The friction and wear properties of Al–25Zn–3Cu alloy were investigated over a range of oil flow rate, pressure and sliding speed using a pin-on-disc machine, after examining its microstructure and mechanical properties. The results obtained were compared with those of a conventional-bearing material (SAE 65 bronze). It was observed that the microstructure of the Al–25Zn–3Cu alloy consisted of aluminium-rich α, eutectoid α + η and θ phases, while the microstructure of the SAE 65 bronze revealed copper-rich α, and eutectoid α + δ phases. It was found that the friction coefficient, temperature and wear volume of both the alloys decreased sharply with increasing oil flow rate and attained almost constant levels beyond a certain range of oil flow rate. It was also found that the friction coefficient and the wear volume of the alloys decreased with increasing pressure, but was observed to be almost independent of the sliding speed. The Al–25Zn–3Cu alloy exhibited higher wear resistance as compared to that of the bronze under all the test conditions. Smearing type of adhesion appeared to be the most effective wear mechanism for the Al–25Zn–3Cu alloy, while abrasion dominated one for the SAE 65 bronze.     

Enhanced wear resistance of Ti-5Al-2Nb-1Ta orthopaedic alloy by nitrogen ion implantation

The tribological properties of nitrogen implanted Ti-5Al-2Nb-1Ta orthopaedic alloy was studied by performing lubricated pin on disc tests against ultra high molecular weight polyethylene pins. The results were interpreted on the basis of friction coefficient, wear volume loss and by characterising the wear debris to understand the wear mechanism. The results indicated a decrease in wear rate for implanted samples. Detailed investigations of the dose dependence on wear performance were carried out. The friction and wear data show a clear transition in wear modes between implanted and unimplanted alloys. The wear debris confirms the presence of titanium oxide and titanium oxynitride phases for untreated and nitrogen implanted alloy.     

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.     

SiCp颗粒复合对ZA27合金滑动摩擦条件下耐磨性能的影响

用铸造法制备了SiC_p/ZA27复合材料,用MM200磨损试验机,测定和对比了基体合金和不同颗粒含量复合材料在不同载重下滑动摩擦的磨损量,结果表明:在重载条件下,复合材料的耐磨性远高于基体材料。此外.还初步分析了不同条件下的磨损机理。