【作者】 刘强；

【导师】 徐仁根；

【作者基本信息】 烟台大学 ， 材料与化工（专业学位）， 2024， 硕士

【摘要】 镓基液态金属是一类常温下为液体的新型合金材料。镓基液态金属具有极低的饱和蒸气压,较高的服役温度,良好的导电、导热性,良好的极压性能和润滑性能,有望作为一种新型润滑剂及润滑添加剂,在高温、空间等极端工况润滑领域具有重要的应用前景。然而,目前对镓基液态金属所能提供的润滑状态及其转变规律缺乏系统认识,以及成分调控对镓基液态金属润滑性能的影响规律尚不明晰。因此本论通过液态纯镓润滑条件下AISI 440C钢自配副的Stribeck曲线和一系列定速摩擦试验,利用SEM、EDS、XPS、XRD等表征手段,系统研究了镓能提供的润滑状态及其转变规律。在此基础上,研究了Zn、Mg、Bi、Cu、Ti和Sc元素的掺杂对其混合润滑性能的影响。结果表明:（1）选用纯镓润滑点接触工况下AISI 440C钢自配副,在法向载荷2～20 N和滑动速度10^-8～1.4 m/s范围内,液态镓只能提供边界或混合润滑,不能形成流体动压润滑;在5 N下的工况下,液态镓所能提供的边界润滑和混合润滑条件下,摩擦副的摩擦系数在0.1～0.3之间,板的磨损率处于10^-8mm³/N·m数量级。（2）润滑初期在接触应力的反复作用下,镓元素被挤压到摩擦界面上与磨屑混合,在正常润滑期间形成了均匀分布（边界润滑）或岛状分布（混合润滑）的富镓膜。在润滑后期,混合润滑的失效主要与富镓膜的再生有关,而富镓膜的再生是由摩擦界面的平均接触应力决定的。（3）掺杂1 wt.%Zn、Bi、Cu、Ti、Sc、Mg元素的镓基液态金属后结果显示:Zn、Bi元素能够完全溶解在镓基液态金属中;Mg元素除部分溶解以外,还生成大量微米级Mg₂Ga₅颗粒;Cu、Ti或Sc元素会生成少量微米尺度的金属间化合物,分别为Cu Ga₂、Ti Ga₃或Sc Ga₃。掺杂1 wt.%的Zn或Cu元素可以改善其润滑性能,而掺杂1 wt.%的Ti、Sc、Mg或Bi元素均会降低镓基液态金属的润滑性能。Zn元素的最佳掺杂量为3 wt.%,摩擦系数较Galinstan润滑时降低12%,磨损率降低50%。掺杂3 wt.%Cu元素使得磨损率较Galinstan润滑时降低49%。（4）摩擦界面处富镓膜的变化对镓基液态金属润滑性能影响的结果表明,掺杂Zn元素促进了镓在摩擦界面上的吸附,从而改善了镓基液态金属的润滑性能;掺杂Bi元素抑制了镓的吸附,降低了镓基液态金属的润滑性能。（5）镓基液态金属中生成的微米颗粒对其润滑性能影响的结果表明,掺杂Cu元素的镓基液态金属润滑性能的提高归功于少量微米尺度Cu Ga₂颗粒的生成。Ti或Sc的掺杂使得镓基液态金属中生成高硬度的Ti Ga₃或Sc Ga₃颗粒,造成三体磨粒磨损。Mg掺杂生成大量的Mg₂Ga₅颗粒,严重破坏镓基液态金属的稳定润滑。更多还原

【Abstract】 Gallium-based liquid metals are a new type of alloy materials that are liquid at room temperature.From the tribological point of view,GLMs have the advantages of extremely low saturated vapor pressure,high operating temperature,good electrical and thermal conductivity,excellent extreme pressure properties and good lubrication properties.They are a new type of lubricant and lubrication additive,and have important application prospects in the field of lubrication under extreme conditions such as high temperature and space.However,there is a lack of systematic understanding of the lubrication state and its transformation law provided by gallium-based liquid metals,as well as the influence law of compositional modulation on the lubrication performance of gallium-based liquid metals.Therefore,this thesis systematically investigates the lubrication state and its transformation law that gallium can provide through the Stribeck curve and a series of fixed-speed friction tests of AISI 440C steel self-mating vice under the lubrication condition of liquid pure gallium,and by using the characterisation means such as SEM,EDS,XPS,XRD,and so on.On this basis,the effects of the doping of Zn,Mg,Bi,Cu,Ti and Sc elements on their hybrid lubrication properties were investigated.The results show that:（1）Pure gallium was chosen to lubricate the AISI 440C steel self-mating pairs under point contact conditions,where gallium could only provide boundary or mixed lubrication in the range of normal loads of 2-20 N and sliding velocities of 10^-8-1.4 m/s,and could not form hydrodynamic pressure lubrication.In the boundary and mixed lubrication regimes,the friction coefficient is between 0.1 and 0.3,and the wear rate is in the magnitude order of 10^-8mm³/N·m at 5 N.（2）In the initial stage of lubrication,under the repeated action of contact stress,the gallium element is extruded onto the friction interface and mixed with the abrasive debris,forming a gallium-rich film with uniform distribution（boundary lubrication）or island distribution（mixed lubrication）during normal lubrication.The failure of mixed lubrication in the later stage of lubrication is mainly related to the regeneration of gallium-rich films,which is determined by the average contact stress at the frictional interface.（3）The gallium-based liquid metal doped with 1 wt.%Zn,Bi,Cu,Ti,Sc and Mg elements will have the following phenomena:Zn and Bi elements can be completely dissolved in gallium-based liquid metals,Mg elements will form a large number of micron-scale Mg₂Ga₅particles in addition to partial dissolution,and Cu,Ti or Sc elements will form a small number of micron-scale intermetallic compounds,which are Cu Ga₂,Ti Ga₃or Sc Ga₃,respectively.Doping Zn or Cu elements on the basis of eutectic Ga/In/Sn can improve the lubrication properties of GLMs,while doping Ti,Sc,Mg or Bi elements all can reduce the lubrication properties.GLM doped with 3 wt.%Zn exhibits the best lubrication properties,with a reduction of 12%and 50%in friction coefficient and wear rate,respectively.Doping 3 wt%Cu in GLM can also effectively reduce the wear rate by 49%.（4）The results of the effect of the change of gallium-rich film at the friction interface on the lubricating properties of gallium-based liquid metal show that doping Zn improves the lubrication properties of GLMs by promoting the adsorption of gallium on the frictional interfaces.Conversely,doping Bi inhibits the adsorption of gallium.（5）The results show the effect of microparticles formed in gallium-based liquid metal on its lubricating properties The improvement of the lubrication properties of Cu-doped GLM is attributed to the generation of a small amount of micron-scale Cu Ga₂particles.The doping of Ti or Sc generates high-hardness Ti Ga₃or Sc Ga₃particles,causing three-body abrasive wear.The doping of Mg generates a large number of Mg₂Ga₅particles,seriously disrupting the stable lubrication.更多还原