| 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. |
PDF Full Text Request