| Cu-Cr alloys have high strength,high conductivity and excellent corrosion resistance,and are used in lead frames and high-speed railways.The softening resistance temperature of Cu-Cr alloy is only 500 °C.In order to further improve the high temperature softening resistance of the alloy,the third component elements such as Zr,Mg,and Ti are usually added to the alloy.In order to explore the effect mechanism of the third element Ti element on the softening resistance of Cu-Cr alloys,this article will take Cu-Cr and Cu-Cr-Ti alloys as the research object,adopting "hot rolling-solution-cold rolling-aging The process of preparing alloy plates,studied the evolution of properties and structure of alloys with different Ti content on different cold-rolled deformations during the aging process,and clarified the strengthening mechanism of the alloy during the aging process.By studying the high-temperature softening performance and precipitation morphology evolution of peak-aged Cu-Cr and Cu-Cr-Ti alloys,the mechanism of Ti to improve the softening resistance of Cu-Cr-Ti alloys is explored.The main conclusions are as follows:Ti element improves the aging hardness of Cu-Cr alloy and delays the decline of aging hardness.The yield strengths of Cu-0.46 Cr and Cu-0.45Cr-0.28 Ti alloys with 80%cold-rolled deformation are similar to 426 MPa and 432 MPa,respectively;while in the peak-aged state,the yield strength of Cu-0.46 Cr alloy decreases to 278 MPa However,the yield strength of Cu-0.45Cr-0.28 Ti alloy rose to 503 MPa.According to the theoretical calculation of alloy strengthening,the theoretical yield strengths of Cu-0.46 Cr and Cu-0.45Cr-0.28 Ti alloys are 299.9 MPa and 497.6 MPa,respectively,which are in good agreement with the experimental values of 278 MPa and 503 MPa.Among them,the solid solution of Ti atoms Strengthening effect and high density of dislocations are the reasons why Cu-0.45Cr-0.28 Ti alloy has high yield strength after aging.After Cu-0.46 Cr alloy is aged at 450 °C for 4 hours,the precipitated Cr phase is mostly spherical or ellipsoidal,and the dislocation density in the matrix is significantly reduced.After the Cu-0.46 Cr alloy is aged for 30 min at the softening temperature of 510 °C,the precipitated Cr phase is still spherical or ellipsoidal,and the matrix has no obvious dislocation entanglement and dislocation wall,and the dislocation density is low,and after aging for 60 min The size of the precipitates increased significantly,reaching 16.5 nm.At this time,the Orowan stress of the spherical precipitates was 50.9 MPa.However,after the Cu-0.45Cr-0.28 Ti alloy was aged at 450 °C for 4 h,the Cr phase was precipitated as a short rod-shaped precipitate,and the dislocation density in the matrix was not significantly reduced.After the Cu-0.45Cr-0.28 Ti alloy is aged for 30 min at the softening temperature of 610 °C,the Cr phase is precipitated as short rod-shaped or ellipsoidal precipitates,and the precipitated phase has a tendency to spheroidize.After aging for 60 min,the Cr particles basically appear as Spherical,with a particle size of about 12.4 nm.At this time,the Orowan stress of the precipitated phase particles is 63.0 MPa,and there are still some dislocations entangled in the matrix.The addition of Ti element can delay the growth of precipitated phases and the decrease of dislocation density during the high temperature aging process of Cu-Cr alloy,thereby increasing the softening resistance of the alloy. |
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