Study On The Properties Of WE43 TPMS Porous Structrue Fabricated By Selective Laser Melting

Mg alloy has the advantages of high specific strength and stiffness,good damping properties,and low elastic modulus,etc.WE43 Mg alloy with the addition of rare earth elements such as Y,Nd and Gd has more excellent biocompatibility,biodegradability as well as similar density and Young’s modulus to human bone compared with metallic biomaterials such as stainless steel,titanium and cobalt-chromium alloy,which is the ideal material for biodegradable bone implants.However,due to the safety problems caused by the flammable and explosive magnesium alloy powder and the material characteristics of small melting and boiling point range and easy oxidation,it is difficult to form the magnesium alloy by Selective Laser Melting(SLM),and the most promising TPMS porous structure in bone implants cannot be formed by traditional manufacturing methods,which seriously hinders the development of magnesium alloy applications in biomedical field..To solve the problem of the small melting and boiling point range of magnesium alloy and the difficulty of forming in additive manufacturing,the process parameters of the forming zone of WE43 magnesium alloy were sought through SLM process optimization,and the forming quality was evaluated based on the surface morphology and relative density.The influence of the process parameters on the microstructure,microhardness and tensile mechanical properties of WE43 magnesium alloy was also revealed,and the melt pool morphology,phase composition and fracture mechanism were analyzed.The SLM process parameters in the forming zone were obtained:laser power 200～225W,scanning speed 800～900mm/s,energy density 74.07～93.75J/mm3,and the best process parameters under comprehensive consideration:laser power 200W,scanning speed 800mm/s.Sheet TPMS porous structures and network TPMS porous structures were fabricated based on the design of different cell types.Also,we adjusted the designed porosity and pore size of TPMS porous structures by changing the structure dimensional parameters.The relationship between TPMS porous structure type and forming quality and compression mechanical properties was also explored.Results show that the network TPMS porous structure has better forming quality and compressive mechanical properties than the sheet TPMS porous structure with the same design porosity,and the sheet TPMS porous structure can withstand large deformation better than the network TPMS porous structure,among which the network TPMS porous structure with P-cell type has the best ability to resist compressive load.This paper explored the in vitro degradation performance of the TPMS porous structure fabricated by SLM for WE43 magnesium alloy,and analyzed the effect of TPMS porous structure type on the in vitro degradation rate.The results indicated that the degradation rate of the network TPMS porous structure was lower.Also,the biocompatibility of SLMed TPMS porous structures was explored by in vitro cytotoxicity test and osteogenesis induction test.The results showed low cytotoxicity during the pre-degradation of the porous structures,but the cell-adherent growth on their material surfaces was poor.