Effect of La2O3 particle size on the microstructure and properties of Al Si alloys deposited via wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) of AlSi alloy deposits exhibits the advantages of a high deposition rate and easy operability, while being suitable for fabricating large-sized metal parts. However, the alloy deposits suffer from various problems such as a large number of pores, coarse and uneven microstructures, and poor mechanical properties. Herein, we added La2O3 powders with different particles sizes (nano-sized, micron-sized, and ordinary-sized particles) to AlSi alloy deposits for optimizing the properties of the specimens. The results show that the surface roughness of the specimens increased with the addition of micron-sized or ordinary-sized particles. However, the addition of nano-sized La2O3 powder improved the forming quality of the alloy deposit, eliminated the slender columnar grains near the fusion line and the central region of the coating, and refined the grains. The addition of La2O3 powder also reduced the maximum texture intensity in the specimen, for which adding nano-sized La2O3 powder had the most obvious effects. In addition, the microhardness and tensile strength of the specimens with nano-sized La2O3 powder were improved, while the average microhardness increased by 13% from 55.2 HV to 62.4 HV. The average tensile strength in the horizontal direction increased by 28% from 172 MPa to 221 MPa, and that in the vertical direction increased by 13% from 135 to 152 MPa. The addition of La2O3 powder was effective in improving the properties of the AlSi alloy deposit. The nano-sized La2O3 powder was the most suitable powder for the WAAM of AlSi alloy.