Achieving high strength Al-Li alloy with minimized element evaporation by wire-arc directed energy deposition

Abstract

Porosity defects and lithium evaporation remain critical challenges in the wire-arc directed energy deposition (WA-DED) of Al-Li alloys. This study develops and validates a dual-surface Gaussian heat source model specifically tailored to the gas tungsten arc-based DED (GTA-DED) process, enabling accurate thermal field simulations. By coupling these simulations with Gaussian process regression (GPR), we systematically investigate the influence of key processing parameters on the deposition quality of AA2195 Al-Li alloy. A novel feature parameter system is introduced to quantitatively evaluate lithium loss—measured at a minimized rate of 1.6 %—and predict dimensional accuracy, which guides the identification of an optimized process window with enhanced formability. Subsequent T8 heat treatment, chosen for its effectiveness in promoting precipitate strengthening, drives microstructural evolution marked by the dissolution of intergranular Cu/Mg-rich phases and the precipitation of dense nano-scale T₁(Al₂CuLi) phases. This transformation leads to a significant increase in yield strength, reaching 554.5 MPa. Despite these improvements, residual defects such as hydrogen-induced pores and shrinkage cavities act as stress concentrators, limiting elongation to 2.2 %. The interplay between strength and ductility is further elucidated through detailed analysis of pore nucleation mechanisms and microtexture evolution. These findings provide critical theoretical insights and empirical data to advance the industrial application of WA-DED processing for Al-Li alloys.