Investigation On Complex Ni-Si Brass By Tuning The Reinforced Phase And Its Influence On Performance

Complex brasses possess excellent mechanical properties and wear resistance,and are widely used in industrial production,especially as an automotive synchronizer ring material,which is valued by the automotive industry.With the higher performance requirements for complex brasses in the industrial field,new complex brasses with nickel-silicon compounds as the strengthening phase have been developed.However,the existing research has very limited knowledge of the nickel-silicon complex brass,especially the research on the mechanism of the strengthening phase and how to effectively control the strengthening phase,which limits the further improvement of material properties.This subject is based on the Cu-Zn-Ni-Si alloy,which studies the changes in microstructure of Cu-Zn-Ni-Si alloy under different Ni-Si content and different cooling rates,and analyzes the effect of Al element on the structure and properties of Cu-Zn-Ni-Si alloy,in order to provide a basis for improving the size,morphology and distribution control of the hard phase in actual production.The results are as follows:?1?The strengthening phase of nickel-silicon brass is Ni₂Si,which has two forms of primary dendrite and eutectic thin rod.The matrix structure is affected by the content of Ni-Si element.When the Ni element and the Si element form the strengthening phase,the remaining elements are dissolved in the matrix and affects the ratio of the?and?phases of the matrix.The solidification rate can obviously affects the size and morphology of the primary phase of nickel-silicon brass.When the solidification speed is slow,the size of the primary phase in the complex nickel-silicon brass increases,and the dendrites of the primary strengthening phase are developed;while when the solidification speed is fast,the size of the primary phase decreases,and the growth of dendrites in the primary strengthening phase is inhibited.?2?The complex nickel-silicon brass without Al addition is composed of?and?phase matrix and?-Ni₂Si hard phase.With the increase of Al content,the matrix of nickel-silicon complex brass gradually transforms to single?phase and the strengthened phase transforms into[Ni?Al?]₂Si.In addition,the 3D morphology of strengthening phase gradually changes from dendritic and fine rod to regular block due to the change of crystal structure and the influence of the crystal-melt interfacial free energy.?3?Adding an appropriate amount of Al element will increase the hardness,yield strength and tensile strength of nickel-silicon brass,which mainly results from reinforcement strengthening.However,the ductility of complex brasses gradually decreases with the addition of the Al content.The fracture mechanism transforms from cleavage failure and micro-voids accumulation fracture to cleavage failure.?4?The wear resistance of complex nickel silicon brass is significantly affected by the strengthening phase and matrix.The wear mechanism of complex nickel-silicon brass under low load is mainly abrasive wear.The wear mechanism of complex nickel-silicon brass under high load is mainly adhesive wear,abrasive wear and delamination wear.The complex nickel-silicon brass with higher hardness can effectively resist adhesive wear and abrasive wear,and the thin rod-shaped eutectic phase has the effect of suppressing crack propagation.The combination of the higher-strength substrate and the regular and uniformly-shaped reinforcement can make the complex nickel-silicon brass have better wear resistance.