Technology And Property Of Nano-SiC Particles Implanted Into Mg Alloy By Laser Shock Wave

Magnesium alloy is widely used in aerospace, automobile, electronics and other manufacture field because of its natures of low specific gravity, high specific strength and other characteristic. But its engineering application is seriously hindered due to its low surface strength, hardness and poor wear resistance. Improving the surface properties of light alloys has become one of the key problems in the fabrication of structural parts. Nanoparticles are widely used in preparation of coating owing to its specialized structure and excellent property. Laser shock peening(LSP) is a new surface treatment technology which has the character of high-power, ultra-fast and ultra-high strain rate. The shock wave generated by LSP can be used as the source of energy for the particles implantation. Combined with the characteristics above, the laser shock peening technology was taken to implanting the nano-SiC particles into AM50 magnesium in this paper. Micro-hardness of the substrate surface and cross section and the friction and wear were investigated. Finite element software ABAQUS was utilized to simulate the first and second dynamic movement of nanoparticles and energy transfer between nanoparticles by laser shock wave. Some important conclusions and research progress of this paper were listed as follows:Firstly, the surface and cross section morphologies after implanting nanoparticles into magnesium alloy via LSP were investigated. And the influence law of particle size on the particle content of the implantation was obtained. SiC particles with dimensions of 60 nm, 100 nm and 200 nm were implanted at laser energy of 12 J, and the surface and cross section morphologies were observed. The results show that nano-SiC particles can be effectively implanted by LSP and the agglomeration can be dispersed. The content of 60 nm SiC particles in the substrate surface layer is more than implanting other size nanoparticles, but when 100 nm and 200 nm SiC particles were implanted by laser shock wave, the laser shock made the nano-SiC particles have better dispersion, more uniform particle distribution and less aggregation.Secondly, micro-hardness and friction and wear properties after implanting nano-SiC particles were investigated. The effect mechanism of laser shock on the wear resistance of magnesium alloy after implantation of SiC nanoparticles was explained. The micro-hardness of the substrate surface after implanted nanoparticles by LSP is 91.7 HV, which is improved by 39.2% and 21.2% compared with the original specimen and laser shock peening specimen, respectively. The friction coefficient of the implanted nanoparticles is lower than that of the laser shock and original specimen. During the process of implanting nanoparticles, the laser shock wave on the surface of the substrate not only induced compressive residual stress, but also refined the surface grain of the substrate, and the hard phase SiC particles were implanted into the surface layer of the substrate by laser shock wave. The wear volume of the implanted nanoparticles is about 12.85×10-3 mm3, which is about only 13.9% of the origin specimen. This suggests that the micro-hardness and wear resistance of magnesium alloy could be improved effectively by the implantation of nano-SiC particles via laser shock wave.Finally, finite element simulation software ABAQUS was employed to investigate the dynamic movement process of nano-SiC particles implanted into magnesium alloy. The depth expression of SiC nanoparticles by laser shock was derived. During this process, the motion of nanoparticles was dispersed, and the surface morphology of the reinforced phase was formed with the increase of time. With the increase of the energy of laser pulse, the depth of the implanted nanoparticles was increased, and accompanied by a lager plastic deformation, meanwhile, the depth of the implantation was increased and nanoparticles were more dispersed. Compared with the penetration of the high-speed penetrator to medium, the expressions of the maximum theoretical depth of first time and second time implanting nanoparticles by LSP were deduced. Compared with the experimental results and analyzed the possible reasons for the errors.In summary, this paper provides a new method for preparing coating on light alloy surface. Furthermore, it also provides a reference for insight into the Mg alloy properties after implanting nanoparticles by laser shock wave. Finally, it provides an important analytical and theoretical basis for understanding the process and depth of the nanoparticles implantation by laser shock wave.