| Copper alloys have been widely used in the production of circuit lead frame materials and electrified train contact lines because of their high electrical conductivity,high thermal conductivity,and corrosion resistance.However,with the rapid development of the electrification road,higher requirements have been placed on the strength and electrical conductivity of the load-bearing cables and electrical contact wires.directionally solidified Cu-Cr-Ti alloys have attracted attention because of the excellent properties of the composite material after deformation.In this paper,Cu-2.5Cr-0.11 Ti hypereutectic alloys,Cu-6.5Cr-0.1Ti hypereutectic alloys and Cu-6.5Cr hypereutectic alloys were prepared using intermediate frequency induction melting furnace and vacuum directional solidification furnace respectively.The evolution of directionally solidified Cu-Cr-Ti hypereutectic alloys after cold work and heat treatment was studied.The influences of tensile rate,deformation amount and ageing temperature on electrical conductivity,tensile strength and softening temperature of unidirectionally solidified Cu-Cr-Ti hypereutectic alloys were investigated by means of resistance measurement and tensile tests;The morphology and composition of the microstructure of the directional solidification Cu-Cr-Ti hypereutectic alloy were analyzed by means of metallographic microscope,scanning electron microscope and energy spectrum analyzer.The research showed that the solidification microstructure evolution of Cu-Cr-Ti alloy after unidirectional solidification is from flat interface,cellular crystal,olumnar crystal to columnar dendrite;When the solidification rate is 5?m/s to 50?m/s,the ?-Cu single phase cytoplasmic structure and the(?-Cu+?-Cr)eutectic tissue alternately grow in the solidified structure.When the solidification rate is 100 ?m/s,the phenomenon of band segregation disappears.The conductivity of Cu-2.5Cr-0.11 Ti hypereutectic alloy with a tensile rate of 100?m/s decreases with the increase of the deformation amount.The aging temperature rises first and then decreases.Conductivity after aging 450°C×1h The rate reaches a peak of 83.73% IACS.Tensile strength increases with the increase in aging temperature,then rises first and then falls,reaching a peak value of 537 MPa at 450°C×1h;The electrical conductivity of Cu-2.5Cr-0.11 Ti hypereutectic alloy with tensile rate of 20 and 30 ?m/s decreases with the increase of deformation,and increases with the increase of temperature at any time,and the tensile strength decreases with the increase of aging temperature.The conductivity of Cu-6.5Cr-0.1Ti hypereutectic alloys with tensile rates of 20?m/s,30?m/s and 100?m/s decreases with the increase of deformation,and increases with the increase of aging temperature.The intensity of the aging temperature rises first and then decreases and reaches a peak value of 546 MPa at 450°C×1h.The post-fault elongation of the Cu-Cr-Ti hypereutectic alloy increases as the time-dependent temperature increases.The softening temperature of Cu-2.5Cr-0.11 Ti hypereutectic alloy is about 547 °C,and the softening resistance of Cu-6.5Cr-0.1Ti hypereutectic alloy is about 550 °C.The innovation of this article is that the microstructure evolution of directionally solidified Cu-Cr-Ti hypereutectic alloy at low tensile rate was studied,the growth mechanism of eutectic phase in Cu-Cr-Ti hypereutectic alloy(?-Cu+?-Cr)was revealed,the evolution law of banded structure in Cu-Cr-Ti hypereutectic alloy at low tensile rate was studied,and the tensile rate range formed by banded structure was established,and a new type of banded structure consisting of ?-Cu phase and low-Cr eutectic phase and high-Cr eutectic phase is found.This banded structure is a supplement to the existing banded structure types. |
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