Effects Of Cold Rolling And Post Heat Treatment On The Microstructure And Mechanical Properties Of Cu-Zr-B Alloys

In this thesis,the Cu-0wt.%Zr-0.08wt.%B、Cu-0.5wt.%Zr-0.08wt.%B、Cu-1.0wt.%Zr-0.08wt.%B and Cu-1.5wt.%Zr-0.08wt.%B alloys were prepared by smelting method.The four alloy samples were subjected to solution treatment,cold rolling with different amounts of deformation and annealing at different temperatures.The microstructures,mechanical properties and electrical conductivity of the samples at different points of the processing were investigated.The strengthening mechanisms and microstructural changes of the samples were also analyzed.The results of the study show that zirconium was not fully dissolved in copper,and there are irregular zirconium diboride particles near the grain boundaries,and the spherical zirconium rich phases are uniformly distributed in the grains.Solute atom Zr can significantly refine the grain,prevent the migration of defects in copper matrix,dislocation slip and achieve the effect of solid solution strengthening,and improve the strength of the alloy.The effect of cold deformation on microstructure and properties of the alloy was studied.The strength of the alloy is obviously improved.When the amount of deformation reaches 60%,the hardness value of the alloy increases slowly,and small angle grain boundaries form inside Cu gains.At this time,the main strengthening mechanism is dislocation strengthening.The microstructure,mechanical and electrical properties of the alloy after aging treatment show that the addition of Zr can delay the recovery of the alloy,inhibit the formation and growth of the recrystallized grains,thereby increasing the temperature of recrystallization.The Cu-0.5wt.%Zr-0.08wt.%B alloys aged at 300℃and 500℃for 1 h is decomposed and precipitated from the matrix as Cu Zr₅,and the phase relationship with the matrix is（（?）0（?））_M//（2（?）（?））and[111]_M//[111]_p.In aging at different temperatures,the strength of the alloy first rises and then decreases.This is because the low temperature aging promotes the precipitation of the second phase,which can effectively pin the dislocations and hinder the dislocation motion.With increasing the annealing temperature,the softening effect of the alloy is higher than that of the precipitation phase,and the strength is lowered.At the same time,the conductivity increases,because the lattice distortion caused by the solid solution atoms is more scattering than the precipitation relative electrons.In this study,the Cu-1.0wt.%Zr-0.08wt.%B alloy at 500°C/1h has good tensile strength and electrical conductivity of 525±3.1 MPa and 79.96±0.19%IACS,respectively.