Study On The Microstructure And Properties Based On Composition Regulation Of Cu-Ni-Sn-P(-Si) Alloy

The influence of different Ni/Sn ratios on the microstructure and properties of Cu-Ni-Sn-P alloys at various stages during heat treatment was studied.Thus,the composition of Cu-Ni-Sn-P alloy was optimized and the deformation heat treatment process was improved.In view of this,the composition ratio and process parameters of Cu-Ni-Sn-P alloy were optimized in this paper,so as to obtain the alloy products with the best comprehensive properties.Three groups of Cu-Ni-Sn-P alloys with different Ni/Sn mass ratios（1:1,1:2 and 2:1）were obtained by vacuum casting.The effects of different Ni/Sn ratios on the microstructure and properties of Cu-Ni-Sn-P alloys at different stages of heat treatment were studied.Three gold combinations cu-Ni-Sn,Cu-Ni-Sn-P and Cu-Ni-Sn-P-Si were prepared based on the optimal mass ratio of Ni to Sn（Ni:Sn=1:2）.The effects of P and Si addition on aging and pre-cooling deformation and aging process on microstructure and properties of Cu-Ni-Sn-P alloy were investigated.The effect of P and Si addition on the high temperature resistance softening mechanism of Cu-Ni-Sn-P alloy was revealed.The main results are as follows:（1）The increase of Sn content can refine the as-cast dendrite of Cu-Ni-Sn-P alloy and inhibit the grain growth during solution process.In the three Cu-Ni-Sn-P alloys with different Ni/Sn ratios,the mechanical properties are the best when Ni:Sn is 1:2.（2）Quantitative calculation shows that the main strengthening method of Cu-Ni-Sn-P alloy is Orowan strengthening.The precipitated phase of1#Cu-1.33Ni-1.35Sn-0.08P alloy is ellipsoidal tetrotetic Ni₁₂P₅,and the orientation relationship with matrix is[001]_Ni12P5//[011]_Cu.The regular spherical precipitates obtained in 2#Cu-0.87Ni-1.82Sn-0.07P alloy are also Ni₁₂P₅,and the precipitates are more evenly distributed.The precipitated phase of 3#Cu-1.78Ni-0.86Sn-0.07P alloy is elongated rod-like phase,which is monoclinic Ni P₂.The precipitated phase of 5#Cu-0.86Ni-1.87Sn-0.07P-0.11Si alloy is a base-core orbicrystal Ni₃Si₂,and the orientation relationship between the precipitated particles and the matrix is as follows:（42 2）_Ni3Si2//（200）_Cu,[001]_Ni3Si2//[1 23]_Cu.（3）The effect of pre-cooling deformation treatment before aging on the microstructure and properties of Cu-Ni-Sn-P alloy was investigated.The pre-cooling deformation treatment has a significant effect on the improvement of the aging properties of Cu-Ni-Sn-P alloy.The peak hardness of 2#Cu-0.87Ni-1.82Sn-0.07P alloy after 70%pre-deformation is 192.3HV and the conductivity is 33.6%IACS.After 70%pre-deformation treatment,the peak hardness of 4#Cu-0.88Ni-1.89Sn alloy is 168.4HV and the conductivity is 29.3%IACS.5#Cu-0.86Ni-1.87Sn-0.07P-0.11Si alloy has a peak hardness of 224.2HV and a conductivity of 36.4%IACS after 70%pre-deformation.（4）The main softening mechanisms of the three alloys at low temperature（400℃～480℃）are recovery and partial recrystallization nucleation,and the main softening mechanisms at high temperature（480℃～540℃）are recrystallization grain growth and precipitate coarsening.The anti-softening temperature of4#Cu-0.88Ni-1.89Sn alloy is the lowest among the three alloys,reaching the standard softening point at 420℃.In the low temperature range（400℃～480℃）,the addition of P element in 2#Cu-0.87Ni-1.82Sn-0.07P alloy reduces the recrystallization ratio greatly,and the anti-softening temperature of 2#alloy reaches 480℃.Meanwhile,compared with 2#alloy,the addition of Si element in 5#Cu-0.86Ni-1.87Sn-0.07P-0.11Si alloy makes the precipitated phase Ni₃Si₂increase the hardness of the alloy and has almost no effect on the softening rate of the alloy,and its anti-softening temperature reaches 520℃.