Research On The Effects Of Si Content On C72500 Alloy Performance

Cu-Ni-Sn alloy is a new type of copper-based elastic materials. Compared with beryllium bronze, it is not only cheaper, with excellent properties and capability to resist the high temperature stress relaxation, but also reducing the size of the component and the green eco-friendly material. The various elastic components can be fabricated and widely used such as in the electronic industry, automobile and appliances. Research result shows that factors influence the Cu-Ni-Sn alloy performance, the important one is the kind of element and its content. In this paper, the C72500(Cu-9.5Ni-2.3Sn) alloy and alloys with different Si content were studied, the effects of Si content on the alloy as-cast microstructure and physical properties, the solution treatment conditions on the organizational structure and physical properties of the C72500alloys and aging treatment on the microstructure and mechanical properties were investigated. The results show that:(1)The dendritic segregation structure is obviously for all of alloy ingot. With the increase Si content (0%-0.3%) in the alloy as-cast, the grain size decrease. The as-cast macro-structure of C72500alloys takes on three different morphologically crystalline regions obviously, the columnar zone as-cast reduces with the enhance of Si; the conductivity and hardness of the C72500alloy as-cast raise with the increase Si content, because C72500alloy with Si not only forms the NiSn and Ni3Sn, but also forms the Ni2Si and Ni3Si, these can strengthen the alloys. The conductivity and hardness of C72500as-cast are9.7%IACS and90.4HV respectively. When the Si content is0.30%in the alloy as-cast, the conductivity and hardness are13.1%IACS and202.5HV, it increases by35.1%,124%respectively for C72500.(2) When the Si content is more than0.15%, the black particles organization is presented after solid solution treatment, this because plenty of tiny Ni31Si12phase occurs during solution treatment. Those Ni31Si12phase occupes the position of the core of grians formation and restrains the grain growth during the solid fication of alloy, so the grain size of alloy as-cast becomes smaller with the increase of Si content (0%～0.3%); the conductivity and hardness of specimens treated at800℃increase with increase the Si content. The conductivity and hardness are affected by solution treatment time; the conductivity of sample treated at800℃×2h is lower than that at800℃×1h, while the hardness is higher.(3)When Si content among0%～0.3%, not only the new phase NiSn and Ni4Sn precipitate, but also the second phase Ni2Si and Ni3Si can be found in specimens aging-treated, plenty of the second phases in the alloy increase with the increase Si content, they can restrict the grain growth and aging precipitation so that strengthen the alloys.(4) The conductivity, hardness and tensile strength of the alloys aging-treated at400℃×4h increase with the increase Si content, when the experimental alloys solution at800℃×2h before aging, the conductivity, hardness, tensile strength are all higher than that solution at800℃×1h. The elongation of alloy decreases with the increase of Si. When the strip of alloy with0.30%Si, solution treatment at800℃×2h, cold rolled with70%deformation and then aged treated at400℃x4h has high conductivity and good properties of strength and elongation, they are16.0%IACS,826MPa and6.8%respectively, correspondingly the conductivity and strength increase by40.4%,28.9%, but the elongation decrease by34%.