Study On Preparation And Strengthening Mechanism Of Multiphase Synergistic Strengthening Copper Matrix Composites

Cu-based composites?CMCs?are functional materials with excellent performance.They have outstanding electrical and thermal conductivity and self-lubricating properties,so they are widely used as electrodes,electrical contact and sliding friction materials.Different types of strengthening phases are widely used in CMCs,such as particle-reinforced phases?SiC,Al₂O₃,TiC,etc.?,fiber-reinforced phases?CNTs,CF,etc.?and two-dimensional sheet-shaped reinforcement phases?graphene,etc.?.Rare earth oxides?such as Gd₂O₃?have excellent thermodynamic stability and can be used as good dispersion-enhancing phases in CMCs.One-dimensional carbon nanotubes?CNTs?and two-dimensional graphene?GNPs?are both new types of nanocarbons.Materials have exceptionally comprehensive properties and are widely used as ideal strengthening phases in CMCs.However,the single reinforcement has limited improvement in the properties of Cu-based composites.In addition,although both CNTs and GNPs are nano-carbon materials,their structures are different,resulting in different properties.Therefore,by combining the advantages of different reinforcing materials,it is expected to achieve the effect of multi-phase synergistic reinforcement and obtain a Cu-based composite material with higher performance.CNTs-GNPs/Cu composites,CNTs-Gd₂O₃/Cu composites,GNPs-Gd₂O₃/Cu composites,and CNTs-GNPs-Gd₂O₃/Cu composites were prepared by electroless Cu plating,internal oxidation and reduction,and vacuum hot-press sintering technologies.Materials.The structure,mechanical properties,and electrical conductivity of multiphase synergistically strengthened CMCs and the various strengthening mechanisms contained in them were analyzed and discussed.The test results show that the synergistic strengthening effect is successfully achieved in all four composite materials,and the strength of the four composite materials is higher than that of a single reinforcing phase reinforced composite under the same conditions.The CNTs-GNPs mesh braided structure was successfully obtained in the CNTs-GNPs/Cu composite.For a certain amount of CNTs-GNPs,changing the addition ratio of CNTs and GNPs has an important effect on the formation of the braided structure.When V_GNPs/V_CNTs=1/6,CNTs and GNPs can form a suitable woven structure.The formation of this structure optimizes the distribution of CNTs and GNPs in Cu,but when the volume fraction of CNTs-GNPs exceeds 1vol.%,aggregation of CNTs and GNPs still occurs in composites.Therefore,for CNTs-GNPs/Cu composites,when the carbon content is 1vol.%and V_GNPs/V_CNTs=1/6,it has the best performance,the conductivity is 86.5%IACS,and the tensile strength is 367MPa.In the CNTs-Gd₂O₃/Cu composite material and GNPs-Gd₂O₃/Cu composite material,Gd₂O₃ particles were synthesized in situ in the matrix by the internal redox method,with a size of about 100nm,which respectively form a mixed reinforcement with CNTs and GNPs.The composite material compared with the CMCs strengthened by a single strengthening phase,the mechanical properties are greatly improved.With the increase of the volume fraction of Gd₂O₃,the strength of the composite material gradually increased with it,and the best value was obtained at 3.5vol.%.The conductivity of 0.75vol.%CNTs-3.5vol.%Gd₂O₃/Cu composite is 79.7%IACS,and the tensile strength is 374MPa.The conductivity of 0.75vol.%GNPs-3.5vol.%Gd₂O₃/Cu composite is 80.1%IACS,and the tensile strength is 381MPa.In the CNTs-GNPs-Gd₂O₃/Cu composite,both in-situ generated Gd₂O₃ particles and CNTs-GNPs braided structure were obtained.The Gd₂O₃ particles mainly played dislocation strengthening in the matrix,and the CNTs-GNPs braided structure mainly load transfer effect.Compared with a composite material having only a single reinforcing phase,the three reinforcing phases in the composite material have a synergistic strengthening effect,and the performance is greatly improved.The performance of 1vol.%?CNTs-GNPs?-3.5vol.%Gd₂O₃/Cu composite material reaches the optimal value,the conductivity is 82.6%IACS,and the tensile strength is 390MPa.The four composite materials include four strengthening mechanisms:load transfer strengthening,fine grain strengthening,Orowan strengthening,and thermal mismatch strengthening.Different strengthening phases have different leading strengthening mechanisms,and each strengthening mechanism and each strengthening phase have synergies.