| Aging-strengthened Cu-Cr alloy has high strength and high conductivity due to the precipitation of nano-precipitated Cr phase,which is widely used in lead frame,high iron contact line and other fields.The precipitation morphology and distribution of Cr phase can be effectively controlled by microalloying,so as to further improve the properties of the alloy.In this paper,Cu-Cr-Ti alloy is taken as the research object to study the precipitation kinetics of Cr phase in Cu-Cr-Ti alloy with different Ti content,and to explore the different interaction of dislocations on Cr precipitates with cubic and spherical morphologies in the matrix after aging of Cu-Cr-Ti alloy,and its influence mechanism on alloy strengthening.Cu-Cr and Cu-Cr-Ti alloy ingots were prepared by vacuum melting,and alloy sheets were prepared by hot rolling-solid solution-aging process.After solution treatment,Cu-Cr and CuCr-Ti alloys were aged at 450 °C,550 °C and 650 °C for 1-100 h,respectively.The precipitation of Cr under different aging processes was observed by transmission electron microscopy(TEM),and the interaction between dislocation lines and Cr precipitates with different morphologies in Cu-Cr-Ti alloy matrix after tension was observed.The main conclusions are as follows:With the increase of Ti content,the aging hardness of Cu-Cr-Ti alloy increases,and the peak aging hardness of Cu-0.52Cr-0.40 Ti at 450 °C reaches 163.3 HV.The aging precipitation kinetic equations of Cu-0.42 Cr,Cu-0.50Cr-0.06 Ti and Cu-0.52Cr-0.40 Ti alloys under different aging processes were obtained.Ti atoms will affect the precipitation of Cr-rich phase,change the interface energy and elastic strain energy.After aging,Cu-Cr-Ti alloy has two kinds of precipitated Cr phases: cubic and spherical.After tensile deformation,the moving dislocations interact with the cubic and spherical Cr phases to bend,and the bending angles are 54° and108°,respectively.The yield strength of Cu-Cr-Ti alloy after solid solution and aging was measured by experiments to indicate that the precipitation phase strengthening increment of the alloy was 183.61±10 MPa.Through the theoretical calculation of the theoretical calculation formula related to the dislocation bending angle,when the cubic precipitated phase accounts for 15 % of the total precipitated phase,the theoretical calculation of the strengthening increment is 181.06 MPa,which is the most consistent with the experimental measured value.The sensitivity analysis of the percentage of cubic Cr precipitates in the total precipitates was carried out to determine whether the parameter has a significant effect on the strengthening of the alloy.The results show that when the total volume fraction of the precipitates is 0.6 %,the sensitivity coefficient is 0.07,indicating that the proportion of cubic precipitates has no significant effect on the strengthening increment.At the same time,the sensitivity analysis of the dislocation bending angle is carried out.By adjusting the standard deviation and variance of the normal distribution,the distribution of the angle is the most consistent with the experimental data when μ=54 and σ=6,and the strengthening increment is also the closest to the experimental value,which indicates that the dislocation bending angle observed by TEM is about 108° and 54°. |
PDF Full Text Request