Microstructure,Properties And Strengthening Mechanisms Of Cu-0.8Cr-0.1Zr Alloy By Thermomechanical Treatment

Cu-Cr-Zr alloy is the most developmental potential copper,and it used in the fields of electronics,electric power,and transportation.However,with the rapid development of modern industry,the performance index requirements for high strength and high conductivity copper alloys are continuously strengthened.This requires us to continuously innovate new Cu-Cr-Zr system alloys on the basis of the original development and develop the corresponding thermomechanical treatment.In this paper,the Cu-0.8Cr-0.1Zr alloy was obtained by melting and casting.The pre-deformation parameters before aging and the secondary cold deformation treatment after aging were studied.The alloy microstructure is observed with the help of optical microscope,scanning electron microscope and transmission electron microscope.The tensile properties at room temperature,hardness measurement and conductivity measurement were used to characterize the microstructure and performance evolution of Cu-Cr-Zr alloys after different thermomechanical treatment.The relationship between structure,properties and process of alloy was established.The research results show that Cu-0.8Cr-0.1Zr alloy is prepared by the process of"cold rolling 60%-solid solution-cold rolling 50%-aging"to prepare Cu-Cr-Zr alloy sheet,the peak-aged alloy hardness reaches 190 HV,and the conductivity is Up to 82.1%IACS.The high hardness（190 HV）of the peak-aged alloy is mainly due to the contribution of dispersion strengthening and dislocation strengthening.After the Cu-0.8Cr-0.1Zr alloy is processed by the process of"melting and casting-hot rolling-solution-cold rolling-aging-cold rolling",the coarse Cr-rich phase still exists in the copper matrix in the form of spherical particles after solution treatment.And after the subsequent cold rolling and aging treatment,it will be distributed along the grain boundary in a long strip shape,and its crystal structure is bcc-Cr phase.The alloy was heat treated at950℃for 1 h,and then cooled in cold water immediately.The cold rolling deformation of alloy is 60%after solution treatment,then cold rolled with 71%reduction after peak aging at450°C.The tensile strength of the alloy were 623 MPa,respectively,and the conductivity was maintained at 74.5%IACS.The calculation and analysis of strength theory found that dislocation strengthening and precipitation strengthening play a dominant role in the strength of the alloy after pre-deformation before aging and secondary cold deformation after aging.The mechanical properties of the Cu-Cr-Zr alloy prepared by the two-step thermomechanical treatment are better than the alloy prepared by the one-step thermomechanical treatment.The primary cause is that two-step thermomechanical treatment is beneficial to the increase of dislocation density,The dislocation density of the two-step thermomechanical heat treatment process is as high as 5.63×10¹⁴m^-2.Aging treatment is carried out after one step of deformation,and recovery occurs during the aging,which makes the dislocation disappear and rearrange,and the dislocation density is reduced,and the dislocation density is 2.2×10¹⁴m^-2.