激光熔化沉积AlSi10Mg及气孔对力学性能的影响

A series of AlSi10Mg alloy walls were additive manufactured by laser metal deposition (LMD) process. The density was above 99%, the tensile strength was more than 350 MPa and the elongation was about 8%. OM and SEM were utilized to observe and analyze the microstructure of as-deposited walls. Results show that even if both of water and oxygen concentration is controlled under 1×10^-5, there are some pores in the microstructure, which means the pores in LMD process are nearly impossible to eliminated. The pores are hydrogen micro pores, with diameter less than 100 μm. Further experiments show that the porosity is closely related to the oxygen concentration. Keeping the temperature and humidity constant, when the oxygen concentration rises from 1×10^-5 to 1×10^-3, the porosity quadruples from 0.45% to 2.71%. Meanwhile the tensile strength decreases more than 100 MPa, falling over 30%, and the elongation reducing by over 20%. Finally, the mechanism of porosity formation was discussed. Methods to fabricate AlSi10Mg alloy with steady mechanical property by LMD process were given.