| High strength copper alloys are widely used in manufacturing mechanical bearings,bearing shells and radiator components because of their excellent mechanical properties,wear resistance and corrosion resistance.The tensile strength of these alloys can reach800-1300 MPa,but the elongation is often less than 5%,which greatly limits the further application of high strength copper alloys.As we all know,there is an inherent contradiction between material strength and plasticity.It is the goal of researchers in the field of materials to improve material strength and ensure good toughness at the same time.In recent years,it has been found that the introduction of twins into Cu-Al alloys with medium and low stacking fault energy can improve the strength and toughness simultaneously,which provides a good reference for the development of materials with both strength and ductility.Therefore,on the basis of Cu-Al low stacking fault energy alloy and adding Ni element,Cu-5.0at.%Al-3.0at.%Ni,Cu-11.0at.%Al-3.0at.%Ni and Cu-16.0at.%Al-3.0at.%Ni alloys are designed and developed in this paper.Nanotwin structure materials are obtained by dynamic plastic deformation and cold rolling,and the microstructure is adjusted by appropriate aging treatment to change the morphology,size and distribution of precipitates,so as to improve the strength and elongation of Cu-Al-Ni alloy simultaneously.In this paper,the effects of Al content changes on the microstructure and precipitate types of Cu-Al-Ni alloy during multistage cold rolling aging treatment and dynamic plastic deformation + aging treatment are mainly studied.Taking cu-11al-3ni alloy as the research object,the effects of cold rolling treatment and dynamic plastic deformation on its microstructure evolution and grain boundary orientation distribution are discussed.The main research results are as follows:(1)After multistage cold rolling aging treatment,the tensile strength of Cu-5.0at.%Al-3.0at.%Ni,Cu-11.0at.%Al-3.0at.%Ni and Cu-16.0at.%Al-3.0at.%Ni alloys are607 MPa,940MPa and 1200 Mpa respectively,while the elongation is 7.7%,6.8% and 10.2%respectively.The tensile strength of Cu-5.0at.%Al-3.0at.%Ni and Cu-11.0at.%Al-3.0at.%Ni alloys treated by dynamic plastic deformation and aging are 624 MPa and 910 MPa respectively,while the elongation is 9.3% and 10.9% respectively.(2)Through TEM analysis of Cu-11.0at.%Al-3.0at.%Ni alloy after multistage cold rolling aging and dynamic plastic deformation aging,it is found that the microstructure of the two alloys is composed of high-density dislocations,various substructures transformed from dislocation structure,nano precipitates and high-density twin lamellae.Comparing the thickness of twin lamella obtained by the two deformation methods,it is found that the thickness of twin lamella after multi-stage cold rolling deformation and aging is about 64 nm,the thickness of twin lamella after dynamic plastic deformation and aging is about 14 nm,and the thickness of twin lamella after dynamic plastic deformation and aging is smaller,which is conducive to the improvement of alloy ductility.For the dislocation density,the dislocation density after dynamic plastic deformation is lower than that after cold rolling.The diffraction pattern calibration results of the precipitates show that the precipitates obtained after two kinds of deformation and aging are B2 Ni Al phase,and the mismatch between the precipitates and the matrix can be determined to be 0.1696 by high-resolution image,and the Ni Al phase maintains a semi coherent relationship with the Cu matrix.(3)EBSD was used to analyze the Cu-5.0at.%Al-3.0at.%Ni,Cu-11.0at.%Al-3.0at.%Ni and Cu-16.0at.%Al-3.0at.%Ni alloy after multistage cold rolling and aging,and the effect of different Al content on deformation was studied..The results show that with the increase of Al content,the proportion of small angle grain boundary increases gradually,from 54.7% to 66.1%.At the same time,it is found that the grain size is refined with the increase of Al content,from 4.2?m gradually decreased to 3.7?m.In addition,it is also found that the increase of Al content has no obvious effect on the twin boundary content,and the number of twin boundaries of the three alloys is basically maintained between 1%-2%.For the three alloys after dynamic plastic deformation aging treatment,the results show that with the increase of Al content,the content of small angle grain boundary gradually decreases,from58.7% to 40.1%.The content of twin boundary increased gradually from 1.8% to 9.7%,and the grain size increased from 3.6?m increased to 4.1?m.Analyze the orientation distribution function of Cu-5.0at.%Al-3.0at.%Ni,Cu-11.0at.%Al-3.0at.%Ni alloy and multistage cold rolled Cu-11.0at.%Al-3.0at.%Ni alloy,shows that with the increase of Al content and strain rate,the main texture of the alloy changes from strong standard Goss / Brass texture({110} <115 >)and s texture({123} < 634 >)to standard brass texture({110} < 112 >).This shows that the strength of brass texture is related to the twin content in the alloy.The higher the content of brass texture,the higher the twin content in the alloy.(4)The strengthening mechanism of Cu-11.0at.%Al-3.0at.%Ni samples after cold rolling and dynamic plastic deformation aging treatment is analyzed.The results show that the high strength is mainly attributed to dislocation strengthening,fine grain strengthening and twin strengthening.The yield strength of Cu-11.0at.%Al-3.0at.%Ni after multistage cold rolling aging is 642.27 MPa,including 356.14 MPa for dislocation strengthening,29.89 MPa for twin strengthening,221.9MPa for grain boundary strengthening,2.84 MPa for precipitation strengthening and 31.5Mpa for solid solution strengthening.The yield strength of Cu-11.0at.%Al-3.0at.%Ni samples treated by dynamic plastic deformation aging is766.47 MPa,including 197.55 MPa for dislocation strengthening,318.28 MPa for twin strengthening,216.7MPa for grain boundary strengthening,2.44 MPa for precipitation strengthening and 31.5Mpa for solid solution strengthening. |
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