The Effect Of Trace Element Si On The Microstructures And Mechanical Properties Of Cu-6Ni-6Sn Alloy

Cu-Ni-Sn alloy is more elastic than beryllium bronze among copper-based elastic conductive alloys.In addition to high strength and toughness,it possesses corrosion resistance,minimal environmental contamination during the preparation process,and a simple manufacturing method.This alloy was frequently employed in connections,relays,and instrument components in its early years.It is the most likely beryllium copper substitute in copper-based elastic materials.Because of its outstanding compressive friction and wear reduction effect,Cu-Ni-Sn alloy has been the primary material of heavy-duty bearings in recent years.It has received a lot of attention because it can fulfill the structural design requirements of a soft and stiff mix of bearing materials.The major application situations are the diesel engine bearings and bushings.However,due to the late research on Cu-Ni-Sn alloy materials,weak basic research,poor industrialization technology ability,and the core key technologies such as the segregation of tin element,the control of discontinuous precipitates at grain boundaries and the uniformity of microstructure in the process of material preparation and processing have not been broken through,engine bearing bushing materials of significant types of equipment in China have long been dependent on imported firms.In light of the aforementioned issues,this paper systematically investigates the effects of different Si content on the microstructure evolution and mechanical properties of Cu-6Ni-6Sn alloy in order to prepare high-performance Cu-Ni-Sn alloy,laying the groundwork for the use of Cu-Ni-Sn material in sliding bearings.The main work and conclusions are as follows:1.The addition of trace element Si to a Cu-6Ni-6Sn alloy can refine dendritic,enhance segregation,and prevent discontinuous precipitation Cu-6Ni-6Sn-0.4Si alloy exhibits superior microstructure than other Si contents when Si is added at 0.4wt%（0wt%,0.2wt%）.2.The addition of trace element Si to Cu-6Ni-6Sn alloy results in the formation of a high melting point Ni₃₁Si₁₂ phase that is easy to precipitate on the grain boundary and occupy the nucleation position of discontinuous precipitation phase in the later aging process,thereby inhibiting later discontinuous precipitation and improving mechanical properties.Pre-cooling deformation prior to aging can result in a significant number of dislocations,and the creation of the second phase Ni₃₁Si₁₂ phase can restrict dislocation movement and achieve the work hardening effect.3.The peak aging process of Cu-6Ni-6Sn-0.4Si is 400℃×1h after adding trace element Si（0wt%,0.2wt%,0.4wt%）to Cu-6Ni-6Sn alloy.At the moment,the alloy’s average hardness value is 355 HV,its average tensile strength is 1100MPa,and its average elongation is 10.5%.4.The grain refinement effect and dislocation cumulative strengthening effect in the matrix progressively decrease when the phase change of Cu-6Ni-6Sn-0.4Si aged at 400°C is studied.However,because the matrix contains nano DO₂₂ ordered phase and L1₂ ordered phase,the precipitation of the second phase and nano ordered phase compensates for the loss of strength,and the elongation achieves its maximum owing to the presence of twins.The quantity of dislocation drops dramatically in the late aging stage of Cu-6Ni-6Sn-0.4Si alloy,and the DO₂₂ ordered phase and L1₂ ordered phase in the matrix continue to coarsen,resulting in rapid expansion of discontinuous precipitation and loss of the alloy’s characteristics.