Study On Hot Roll Bonding Process And Properties Of Cu/Mo/Cu Clad Sheets

The Cu/Mo/Cu clad sheets have great application prospects due to its adjustable thermal expansion coefficient and thermal conductivity and excellent mechanical properties.It is the hot issues to manufacture the Cu/Mo/Cu clad sheets through reasonable rolling processes and establish the relationship between its microstructure and properties.In this paper,pure copper and pure molybdenum were selected as raw materials,and Cu/Mo/Cu laminated composite plates were fabricated in a single pass with different rolling reductions.The interface evolution,cooperative deformation and the inhomogeneous microstructure of the component metals caused by the cooperative deformation under different rolling processes were analyzed.The mechanical properties and thermal properties of the clad sheets were studied by tensile,thermal expansion and thermal conductivity tests.Combined with the finite element simulation method,the thermal expansion property of the clad sheets was studied.The rolling reduction has an important influence on the interface morphology of Cu/Mo/Cu clad sheets.Larger rolling reduction contributed to the sound combination of interface.When the reduction was 70%,the bonding interface was continuous and no oxides were visible.The increased rolling reduction and rolling temperature contribute to the coordinated deformation of Cu and Mo.As the rolling reduction increases,the grain size of the Cu layer gradually decreased,and the internal small-angle grain boundaries gradually increased.The middle area had a larger grain size than the near-interface and near-roller areas.When the reduction reached to 70%,the grains were distributed along a shear band which is the direction of about 20~oto RD.The Mo layer mainly contained{100}<uvw>and{111}<uvw>textures,and the textures of the near-interface area and the middle area are obviously different.The inhomogeneity of the structure is caused by the friction between Cu and the roller and the uncoordinated deformation between copper and molybdenum.As the rolling temperature rised,the Cu layer grains increased and the angle between the shear band and the RD direction gradually increased.The texture strength of the Mo layer gradually weakened,and the textures of the near-interface area and the middle area were significantly different.With the increase of the rolling reduction,the strength of the clad sheets gradually increased,and the elongation gradually decreased.As the rolling temperature increases,the strength of the composite plate gradually decreases and the plasticity increases.The thermal expansion coefficient of the clad sheets decreases with the increase of the volume fraction of the Mo layer.The thermal conductivity of the clad sheets is related to the interface morphology and the volume fraction of component metals.When the interface is tightly bonded,the higher thermal conductivity is related to the larger volume fraction of the Cu layer.After annealing at 400 ~oC for 1 h,due to the elimination of the internal stress of the clad sheets and the recovery and recrystallization of the Cu layer grains,the strength of the samples under different rolling processes decreased and the plasticity increased,and the annealing contributes to the improvement of the thermal conductivity.In this paper,the thermal conductivity of 193.16 W/(K·m)can be obtained by the rolling temperature of 950 ~oC and reduction of 70%then annealing.The finite element simulation results indicate that the terminal face of the clad sheets was sunken inward.Most area of Cu and Mo layers can achieve sound co-deformation under the thermal load and concentrated stress and strain only appeared in the end face on two sides.As the Cu/Mo layer thickness ratio increases,the thermal expansion coefficient of the clad sheets gradually increases.The internal equivalent stress of the Mo layer gradually increases,but the equivalent stress of the Cu layer gradually decreases.By the combination of numerical simulation and theoretical calculation,a model of the thermal expansion coefficient of the Cu/Mo/Cu clad plate is established,which can predict the thermal expansion coefficient and provide a theoretical basis for the engineering application of the Cu/Mo/Cu clad plate.