Formation And Characteristic Evolution Of Periodic Microstructures On Ti6Al4V Surface Induced By Nanosecond Pulse Laser

Taking excellent mechanical,physical,and chemical properties,Ti6Al4V has been widely employed in national defense,aerospace,biomedical and other fields.However,some shortcomings,such as high friction coefficient,low hardness and wear resistance,limit its industrial applications to some extent.As a typical method of surface modification,laser surface microstructure processing has become a research hotspot at home and abroad due to its unique advantages such as environmentally friendly,flexible and efficient,and improves its potential applications.However,there are some difficulties at the present stage,including the inconsistency of the microstructure formation mechanism,the lack of large-area preparation methods,and poor mechanical robustness of the surface microstructure.On this basis,this paper attempts to use nanosecond lasers to prepare large-area periodic microstructures on the Ti6Al4V surface.The specific research contents are as follows:Firstly,the paper attempts to irradiate the Ti6Al4V surface using nanosecond pulse laser in nitrogen.And two typical periodic microstructures,namely porous structure and LIPSS,were successfully prepared on Ti6Al4V surface.The influence of laser parameters including laser power,repetition frequency,scanning speed,and overlap rate on the evolution of these two structures was studied.Based on basis,the parameters of the large-area preparation of the two microstructures were optimized,and the formation mechanism was analyzed.At the same time,the porosity of the porous structure was adjusted by changing the laser parameters,and the space period of LIPSS was adjusted by changing the incident laser angles.Secondly,the theoretical analysis and numerical simulation were further studied for the LIPSS prepared by nanosecond laser on the Ti6Al4V surface.Comprehensive analysis on the theoretical basis of Plasmon,Drude model,and Dual temperature model,combined with comparative experiments under argon atmosphere and energy dispersive X-ray analysis and X-ray diffraction characterization results,an interference coupling model of incident laser and plasma was established to explain the formation principle,and the influence of the thermal effect of nanosecond laser on the formation of LIPSS was also analyzed.On this basis,the space period of LIPSS under different laser incident angles was calculated,and the change of the space period with the laser incident angle was predicted.Through the finite element analysis software,the Dual temperature and the simulation model of the excited SPP on the Ti6Al4V surface was established,which further explains the excitation and propagation of SPP in the formation mechanism of LIPSS.After that,the surface properties of the prepared large-area periodic structures were characterized and analyzed.A contact angle measuring instrument was used to characterize the surface wettability,and the nano-indenter and scratch instrument were used to characterize the surface mechanical properties.Additional structural color characterization for the LIPSS was carried out.The large-area porous structure and LIPSS have improved the hydrophilic and hydrophobic properties of the Ti6Al4V surface before and after chemical modification.The surface hardness of porous structure and the original Ti6Al4V remain the same.The LIPSS enhance the hardness of the Ti6Al4V surface and reduce the friction coefficient of its surface.To sum up,nanosecond pulse lasers were used to prepare two typical periodic microstructures on the Ti6Al4V surface,and the evolution process and regular of different laser parameters were studied,and obtained the large-area preparation process parameters of the two microstructures.The formation mechanism was studied by theoretical analysis and numerical simulation,and the surface properties of the prepared large-area periodic structures were characterized.The research results enhance the understanding of the nanosecond laser-Ti6Al4V surface interaction process and mechanism,and have practical significance for enriching the functional applications of Ti6Al4V.