Mechanical behavior of Al6061 produced by laser powder bed fusion: Effects of heat treatments and strain rates

Al6061 is an important structural alloy, but its processing by additive manufacturing (AM) is challenging due to high porosity and cracking susceptibility. In this study the effects of heat treatment (direct aging (DA), annealing, T6, and hot isostatic pressing (HIP)) and strain rate on the microstructure and mechanical behavior of porous PBF-LB Al6061 were investigated. Split-Hopkinson pressure bar (SHPB) was used in dynamic compression experiments at strain rates from 5x10 2 to 1.8x10 3 s −1 , while quasistatic tests performed at strain rates 1x10 −4 and 1x10 −3 s −1 . Microstructural analyses revealed that as-built and all heat-treated conditions had significant porosity (∼3.5–5 %), and there were no consistent changes in grain size or texture. Microhardness and compression tests showed that as built and DA specimens had the highest hardness and flow stresses. In contrast, annealed, T6, and HIP conditions caused softening, and HIP specimens showed the lowest strengths. Under dynamic compression, all specimens exhibited increased flow stress compared to quasistatic loading, with strain rate sensitivities ranging from 12 % in the as built to 27 % in annealed specimens. In addition, all specimens had lower Poisson's ratio under dynamic loading compared to quasistatic loading. These findings show the limited effectiveness of conventional post-processing strategies in eliminating porosity or improving strength in PBF-LB Al6061. • As-built and heat-treated PBF-LB Al6061 show 3.5–5 % porosity. • Direct aged (DA) and as-built specimens give highest hardness and flow stress. • Annealing, T6, and HIP cause significant softening. • Dynamic loading increases flow stress vs. quasistatic loading. • Lower Poisson's ratio is observed under dynamic compression.