| The surface of alloying Nb/Cu based on TC4 alloy was studied by high current pulsed beam irradiation technology(HCPEB).The phase composition,microstructure on the alloyed surface of samples were investigated systematically with X-ray diffraction(XRD),optical microscope(OM),Laser Scanning Confocal Microscope(LSCM),scanning electron microscope(SEM)and transmission electron microscopy(TEM)under different times of irradiation.At the same time,the microhardness,friction and wear,and electrochemical corrosion properties of the alloyed samples were tested.By establishing the internal relationship between the microstructure state and performance,the surface alloying mechanism and modification mechanism were analyzed and summarizedIn order to improve the surface properties of TC4 alloy,the surface of TC4 alloy was Nb alloyed by HCPEB technology.Eruptive craters were formed on the surface of HCPEB irradiated samples,and their density and size decreased with the increase of alloying times.The alloying element Nb was melted to form a uniform and dense alloy layer on the matrix.The thickness of the alloy layer after 40 irradiation treatments was 3.6 μm.The alloy layer was characterized in detail using different methods.The structure of the alloy layer was mainly composed of α’-Ti martensite and β-Ti equiaxed grain.In addition,NbTi4 particles also existed in the alloy layerThe mechanical alloying(MA)and HCPEB irradiation technology were used to achieve Cu alloying on the surface of TC4 titanium alloy.The alloyed layer was successive and dense after 30-time irradiation,and the thickness was 4.5 μm According to the analysis of micromorphology,the alloy layer was mainly composed of α’-Ti martensite,β-Ti and CuTi2 with a size of 2～5 μm.After HCPEB irradiation treatment,the grains on the surface of the material were refined,and the existence of nanocrystals was observed.In addition,there are high-density crystal defects such as twins and dislocations insideCompared with the original samples of TC4 alloy,the surface microhardness test results show that the microhardness values of the samples after Nb/Cu alloying treatment with HCPEB irradiation were improved,mainly due to the comprehensive effect of strengthening mechanisms such as solid solution strengthening,fine grain strengthening,and dispersion strengthening.Meanwhile,the tendency of the surface hardness values of the samples increased with the increase of the irradiation timesThe friction and wear test results show that the friction coefficient and wear rate of the samples after HCPEB irradiation Cu/Nb alloying treatment are significantly reduced compared with the original sample,and the value decreases with the number of irradiation,indicating that the surface friction and wear performance has been improved after irradiation treatment,which is closely related to the reduction of the surface roughness of the sample,the increase of the surface hardness,and the increase of the thickness of the alloyed layerThe results of the electrochemical corrosion test showed that the corrosion resistance of the alloyed material after irradiation was significantly improved compared with the original sample.The promotion of the corrosion resistance was mainly due to the refinement of the grains on the surface of the sample during the irradiation process and the significant increase of grain boundaries,providing more channels for the rapid diffusion of atoms,which leads to the formation of a denser oxide film on the surface of the alloy.In addition,the craters and homogenization of the sample surface have an important effect on the compactness of the oxide film during the irradiation process.Besides,the formation of oxides(such as Nb2O5)is also an important factor in improving the passivation film on the surface of the material in order to improving the corrosion resistance. |
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