Effect of silver microalloying on microstructure and crack inhibition of AA2195 aluminum-lithium alloy fabricated by laser powder bed fusion

Abstract

Additive manufacturing (AM) of aluminum alloys has been widely employed in aerospace, automotive, and other high-performance engineering applications. Nevertheless, aluminum-lithium (Al-Li) alloys processed via laser powder bed fusion (LPBF) are susceptible to solidification cracking and often exhibit suboptimal mechanical properties. In this study, the effects of silver (Ag) microalloying on the microstructure, crack formation, and tensile properties of LPBF-fabricated AA2195 alloy at room temperature were systematically investigated. An amount of 2.5 wt.% Ag was introduced into 2195 alloy powders via ball milling, and its influence on microstructure evolution and grain morphology was analyzed. The results indicate that Ag significantly reduces crack density while promoting the transformation from columnar to equiaxed grains. This may be attributed to the heterogeneous nucleation of Ag-Cu-Mg and Ag-Cu clusters. Meanwhile, Ag addition promotes the precipitation of θ' (Al2Cu) and T1 (Al2CuLi) phases, which contributes to enhanced precipitation strengthening. As a result, the Ag-modified alloy exhibits an ultimate tensile strength of 289 MPa at room temperature with elongation increased by approximately 60% compared to the unmodified alloy. The incorporation of Ag also improves the overall defect tolerance and fracture resistance of the alloy, attributed to combined effects of grain refinement, precipitation strengthening, and enhanced microstructural homogeneity. This work provides new insights into compositional design for producing crack-free, high-performance Al-Li alloys via LPBF and demonstrates the significant potential of Ag microalloying for enhancing their mechanical properties.