Study On Electrodeposition Process And Tensile Properties Of Micro/Nano-Scale Copper-and Nickel-Based Composites

Micro/nano-scale copper-and nickel-based composites have great application and research significance for electronic packaging,automotive and aerospace fields.In the first part of research,electrodeposition technology is used to change the current waveform,stirring mode,current density as well as the concentrations of graphene oxide(GO)to electrodeposit reduced graphene oxide/copper(RGO/Cu)composites.The effects of process parameters on the distribution of RGO in Cu matrix,the variation of grain size and the tensile properties are studied.Otherwise,Ni composites with nano mutilayer structures are successfully deposited by periodically changing the current density and deposition time.The strengthing mechanism of layer thickness ratio and grain size ratio on the tensile properties of multilayer Ni composites are studied.The mixing rule is used to quantitatively calculate the extra stress,extra work hardening rate and extra elongation due to the "interfacial coupling effect" in multilayer Ni composites.The mechanism of tensile deformation and fracture of multilayer Ni composites is studied.RGO/Cu composites with a thickness of 100 ?m is successfully deposited by using graphene oxide(GO)as reinforcement addtive.The optimized conditions of electrodeposition are:GO concentration of 0.2 g/L,ultrasonic assistant,reverse pulse,and forward current density of 5 A/dm2.The deposited RGO/Cu composite under the best parameters condition has dense structure and few defects,and GO is directly reduced to RGO in the electrodeposition process and uniformly distributed in the Cu matrix.The grain size of RGO/Cu composite is 0.47±0.26?m.RGO has a heterogeneous nucleation effect on Cu matrix to refine the grains.The yield strength and ultimate tensile strength of the composite are 341±39 MPa and 398±68 MPa,respectively.And uniform elongation and fracture elongation are 8.3±1.9%and 20±2.0%,respectively.The strengthening mechanism in the RGO/Cu composites caused by RGO particles are grain strengthening and Orowan strengthening.Compared with electrodeposited Cu with preferred orientation,RGO makes the crystal orientation of Cu-based composites more random.By periodically changing the electrodeposition current density and deposition time,multilayer Ni composites with different layer structures are successfully prepared.When the current density of adjacent component layers is 100 and 30 mA/cm2,the grain size of the prepared adj acent component layers is 27±9 nm and 7±11 nm,respectively.The layer thickness ratio prepared by changing the deposition time is 3:1.Multilayer Ni composite deposited under the above conditions has the best comprehensive mechanical properties.Its yield strength is 1512±101 MPa,ultimate tensile strength is 1843±56 MPa,.uniform elongation is 3.14±0.2%,and fracture elongation is 9.5±1.8%.Compared with single component Ni,multilayer Ni composites with different layer structures have a good combination of strength and plasticity.The interfacial coupling effect caused by the cooperative interaction between mechanically incompatible layers in multilayer Ni composites will significantly change the tensile properties,which can effectively improve the elongation and work hardening ability.The extra work hardening rate of multilayer Ni composites are provided by the extra stress and gradually reduced with the increase of strain.The extra work hardening rate and extra stress increase with the decrease of grain size ratio and layer thickness ratio.Interfacial coupling is not necessarily beneficial to the composites and even make the decrease of strength of the multilayer Ni composites,which will introduce more defects or the difference in grain size between adjacent layers will cause a large interface mismatch.The fracture mode of multilayer Ni composites is composite fracture with shear bands and dimples.