【作者】 刘勇；

【导师】 刘平；

【作者基本信息】 西安理工大学 ， 材料学， 2007， 博士

【摘要】 针对我国高速电气化铁路对接触线用材料提出的性能要求,研制和开发了新型接触线用稀土微合金化高强高导Cu-Cr-Zr(-RE)合金材料,并对其时效析出特性进行了研究。采用相对电阻率γ和其变化量?γ作为评价时效过程的参数,基于动态电阻法对合金等温加热和等速(变温)加热时效析出动力学进行了研究。研究表明:随等温时效温度升高,孕育期缩短,?γ的增加速率呈现上升趋势;合金在等速加热时效时,加热速率较小则?γ较大,而加热速率越大则时效过程开始和结束的温度也越高。对比研究了几种合金时效析出行为和强化机理,研究发现:固溶态合金进行时效处理时,时效初期显微硬度和导电率均大幅上升,Cu-Cr-Zr合金经480℃×2 h时效后显微硬度和导电率分别为106 HV和72.8%IACS;对固溶态合金施以冷变形后,可为析出相的形核及生长提供有利条件并加速时效析出过程的进行,同时会出现析出和再结晶两个过程,二者交互作用会对时效后组织和性能产生影响,Cu-Cr-Zr合金经固溶-60%变形-480℃×1 h时效后性能为154 HV和83.5%IACS;添加微量RE后,相同时效处理后合金显微硬度比Cu-Cr-Zr合金高出约15~20 HV,而导电率则降低约2%~4%IACS,同时改善了Cu-Cr-Zr合金高温性能,其抗软化温度提高约30~40℃;微观分析表明,合金的时效析出强化,是由在铜基体上析出体心立方晶格的Cr和面心立方CrCu2(Zr,Mg)两种析出相共同作用造成的;研究提出了合金接触线加工工艺,加工后线材力学性能达到:抗拉强度,605.6 MPa;导电率,80.8 %IACS;延伸率,10.2 %。完全满足高速电气化铁路对接触线高强(≥550 MPa)、高导(≥80 %IACS)及延伸率(≥5 %)等方面的要求。在采用矩形梁弯曲试验进行应变分布测试结果的基础上,首次利用勒让德多项式作为裂纹柔度法中的插值函数对合金线材残余应力大小及分布进行了计算。经固溶-时效-变形处理后合金残余应力将发生释放并降低到约-50 MPa~30 MPa范围内。在自制电磨损实验机上对合金导线进行了电滑动磨损试验:相同试验条件下,三种Cu-Cr-Zr-RE合金耐磨性均优于Cu-Cr-Zr合金,其中又以Cu-Cr-Zr-Ce合金耐磨性最好;随着载流强度的增加,RE对Cu-Cr-Zr合金耐磨性能的改善作用有所下降;SEM观察和EDS分析均表明,未加电流情况下,合金的滑动磨损形式有粘着磨损、磨粒磨损和疲劳磨损,其中疲劳磨损为其主要磨损形式,而在载流磨损条件下,合金的磨损增加了电烧蚀磨损形式;研究发现在磨损表面下的亚表层中发生了再结晶现象,同时产生一个与磨损表面相垂直的拉应力分量,该应力将促进亚表层中裂纹的形成及扩展、加速合金的磨损过程。首次在本实验条件下,建立了接触线-滑块电磨损的物理模型和数学模型。更多还原

【Abstract】 According to the properties of contact wire used materials of high-speed electrical railway, a new series trace alloyed Cu-Cr-Zr(-RE) contact wires with high strength and high electrical conductivity were developed and manufactured. The aging precipitation behavior of the alloys was investigated in this paper.The relatively electrical resistance ratio, such as theγvalue or the ?γvalue which was defined the change of theγvalue as the parameters, was used to estimate the kinetics of isothermal-heating and iso-speed-heating aging precipitated by using the dynamic resistance method. The results showed that the incubation period was shortened and the increased velocity of the ?γvalue gone up with the increased isothermal-heating aging temperatures. The ?γvalue would be rather higher with the less heating ratio, and the aging beginning and finishing temperatures would rise with the rapid heating ratio in the iso-speed-heating aging process.The aging precipitation behavior and the strengthened mechanism of these tested Cu-Cr-Zr(-RE) alloys were studied contrastively. The hardness and electrical conductivity values of the solution treated alloys would rise rapidly at the beginning of the aging process. And the values of hardness and electrical conductivity of the Cu-Cr-Zr alloy are 106 HV and 72.8%IACS after aged at 480℃for 2 h, respectively. The cold deformation could offer advantages for the precipitated phase to nucleate and develop, and could accelerate the precipitated course of the solution treated alloys. After soluted-60% deformed-aged at 480℃for 1 h treatment, the values of the Cu-Cr-Zr alloy would be increased to 154 HV and 83.5%IACS, respectively. With the trace RE addition, the values of the hardness and the soften temperature could increase 15~20 HV and 30~40℃, respectively, while that of the electrical conductivity would dropped about 2%~4%IACS. There are two courses, such as precipitation and recrystallization, would occur in the aging process, and the interaction between these two courses would influence the structures and performances of the aged alloys. The precipitated phases from the Cu matrix, such as Cr phase with the b.c.c pattern and CrCu2 (Zr,Mg) phase with f.c.c pattern, could bring the synergetic effect on aging precipitated strengthen. TheCu-Cr-Zr(-RE) alloy contact wire process technics were put forward. The mechanical properties of the contact wire, such as tensile strength, electrical conductivity and yield strength could achieve 605.6 MPa, 80.8 %IACS and 10.2 %, respectively. These values exceeded completely the requirements (tensile strength≥550 MPa, electrical conductivity≥80 %IACS and elongation≥5 %) for the contact wire which be used in the high-speed electrical railway. According to the strain distribution test data through the rectangle bent beam test, the crack compliance method (CCM) using Legendre polynomials as the interpolation was employed firstly to measure the residual stresses distribution in the alloys wire. The residual stresses would release and the values of these would be dropped into a low level range about -50 MPa to 30 MPa after soluted-aged-deformation treatment.The electrical sliding wear resistance tests were performed on the eletrical wear resistance testing machine made by the lab. The wear resistance performances of the three Cu-Cr-Zr-RE alloys were all better than that of the Cu-Cr-Zr alloy under the same experimental condition, and that of the Cu-Cr-Zr-Ce alloy was the best. The effect of RE elements on improving the wear resistance property would be decreased with the increased electrical currents. Using SEM and EDS, the analyzed results showed that the sliding wear mechanism of the Cu-Cr-Zr alloy were made up of adhesive wear, abrasive wear and fatigue wear without current in which fatigue wear was the dominating mechanism. While adhesive wear, abrasive wear, fatigue wear and arc erosion would be the wear forms under currents. The recrystallization occurred in the subsurface in the tested process. Meanwhile, a tensile stress with vertical orientation to the surface was taken place, and this stress would accelerate the formation and propagation of the crack in the subsurface, then the alloys wear would be serious. The electrical sliding wear physical and mathematical model between contact wire and slide block based on this research was presented.更多还原