Effect Of Heat Treatment Process On Mechanical Properties And Microstructure Of Cu-Ni-Sn Alloy

Cu-Ni-Sn alloy is a late-model elasticity copper alloy without pollution and has excellent comprehensive properties.In the early stage,it was mainly used as a high elastic conductive material to replace beryllium bronze.In recent years,it has been used as a heavy duty bearing alloy material and received widespread attention.However,up to now,the detailed preparation process and technology of the high performance Cu-Ni-Sn alloy and its products which can meet the harsh working conditions are strictly blocked in China,and the specific preparation and processing details and process parameters are unknown.Therefore,it is necessary to carry out research on the heat treatment process of Cu-Ni-Sn alloy.This paper takes hot extruded Cu-Ni-Sn alloy is taken as the research object.From the perspective of microstructure and macroscopic mechanical properties,the analysis and optimization of heat treatment process parameters are carried out.The main work is as follows:In this paper,the effects of different heat treatment process parameters on hardness,strength,plasticity and toughness were studied by using L₁₆(4³)orthogonal test design with the following process parameters:solution temperature,aging temperature and aging time as the research factors.The results show that with the increase of solution temperature,aging temperature and aging time,the hardness and strength first significantly increased and then decreased,while the elongation first decreased and then increased.The optimal combination of process parameters to ensure high strength and hardness is 775?solution×1h+water quenching+380?aging×5h(water-cooling).The influences of the process parameters of solution treatment and aging treatment on physical performance should be as follows:aging temperature>aging time>solution temperature.After optimization,the hardness is increased by 110%,the tensile strength is increased by 84.8%and the yield stress is increased by 175.3%.The fine texture and physical properties of Cu-Ni-Sn materials after thermal treatment at different temperatures were investigated.The following conclusions were obtained:at775?×1h,the solute Sn element was completely dissolved in the?-Cu matrix and the grain size was uniform.At 380?×5h,the strengthening phase particles are uniformly distributed at the grain boundary.At this time,the mechanical properties of the alloy are the best,and the hardness is 269HB,the tensile strength is 865MPa,and the yield strength is 757MPa.The analysis of the tensile section morphology at room temperature shows that the fracture mode is ductile fracture at 320?,brittle fracture at 380?,and ductile fracture at 400?.