Hot deformation induced microstructural evolution in local-heterogeneous wire + arc additive manufactured 2219 Al alloy

This study investigates the hot deformation behavior and relative microstructural evolution of a wire + arc additive manufactured (WAAMed) 2219 Al alloy, in which hot compression was conducted in the temperature range of 300–480 °C at the strain rates of 0.01–10 s⁻¹ with a true strain of 60%. The local-heterogeneous microstructure shows an alternated distribution of equiaxed and columnar grains. The θ′ phase precipitates near the grain boundaries owing to heat accumulation. These microstructural characteristics lead to a higher stress resistance during hot deformation as compared to as−cast and wrought 2219 Al alloys. The calculated activation energy for the WAAMed 2219 Al is 161.1 KJ/mol, slightly higher than that of the as−cast sample. The proportion of low-angle grain boundaries is 70–80% in the as−deformed WAAMed 2219 Al alloy, which is mainly attributed to the dynamic recovery behavior with an auxiliary dynamic recrystallization. Additionally, the dynamic recrystallization grains fraction increases with a decrease of the Zener-Hollomon parameter. With a constant strain rate and an increased deformation temperature (300–480 °C), the micro-hardness firstly decreased and then gradually increased. The nanoindentation results show that the influence of hot deformation conditions on the elastic modulus of the hot deformed WAAMed 2219 Al alloy is not obvious.