Effect Of Cr And P On Microstructure And Properties Of Cu-Ni-Ti Alloy Resisting High Temperature Softening

High-strength,medium-conducting copper alloys have excellent all-round properties such as high strength,high elasticity and electrical,thermal and creep resistance,and are used in a wide range of applications such as resistance welding electrodes,crystalliser linings,relays,electrical connections and springs,and fastening elements.The rapid development of science and technology has placed higher demands on copper alloys that combine strength,electrical conductivity and resistance to softening.In this paper,Cu-Ni-Ti alloy was prepared by conventional melting and casting and heat treatment processes,focusing on the influence of Cr and P elements alone and together on the microstructure and properties of Cu-Ni-Ti alloy,and exploring the combination of elemental micro-alloying and solid solution aging to enhance the performance of Cu-Ni-Ti alloy,and obtaining a Cu alloy with high hardness,high softening temperature and good electrical conductivity.Cu alloy material with both high hardness,high softening temperature and good electrical conductivity,the main results are as follows.The addition of Cr alone enhanced the hardness of Cu-Ni-Ti alloy and reduced the electrical conductivity and softening temperature,while the addition of Cr significantly refined the as-cast and solid-solution structure of Cu-Ni-Ti alloy.age-hardening characteristics,i.e.hardness rises and then falls,conductivity rises and then stabilizes,and as the Cr content increases from 0 to 1.0 wt.%,the peak ageing hardness of the alloy increases significantly,conductivity decreases significantly,and the softening resistance temperature decreases from700°C to 650°C.After TEM microstructure analysis,it is determined that its main age-strengthening phases are the nano-sized Ni Ti and Cr phases,and during the high temperature During softening,the nano-precipitated phases grew significantly and underwent significant recrystallisation.Compared to the Cr phase,the Ni₃P phase precipitates less solute elements in Cu-2.8Ni-1.2Ti alloy,resulting in a higher electrical conductivity than Cu-2.8Ni-1.2Ti.This results in a higher electrical conductivity than the Cu-2.8Ni-1.2Ti alloy.The aging results show that the Cu-2.8Ni-1.2Ti alloy has excellent properties with a hardness of 166.4 HV and a conductivity of 52.4%IACS at a P content of 0.2 wt.%.The high temperature softening results show a softening temperature of 700°C.The addition of trace Cr and P elements not only refines the Cu-2.8Ni-1.2Ti as-cast and solid solution alloy,but also significantly increases the number and size of the second phase in the microstructure.The aging properties results showed that the Cu-2.8Ni-1.2Ti alloy had excellent property at 0.2 wt.%P and 0.7 wt.%Cr,but there was no significant difference when compared with the Cu-2.8Ni-1.2Ti-0.7Cr alloy.The alloy was subjected to double aging and pre-deformation process,and the influence of different deformation amounts on the alloy’s property was investigated,and the optimum deformation amount was determined to be 60%,the properties were significantly improved with a hardness of 220.6 HV,conductivity of 51.6%IACS and high temperature softening results showing a softening temperature of 650°C.