In situ EBSD analysis of the deformation mechanisms of a Zn-1wt%Mg alloy manufactured by laser powder bed fusion

The deformation mechanisms of a Zn-1wt.% Mg alloy fabricated by laser powder-bed fusion were investigated by in situ mechanical tests within the scanning electron microscope combined with electron backscatter diffraction. Fully dense samples with a relative density of ∼99.95% were produced using optimized processing parameters. The microstructure consisted of fine equiaxed α-Zn grains (average size ∼2.8 µm) with a weak crystallographic texture, along with a eutectic network of α-Zn + Mg₂Zn₁₁ located primarily at grain boundaries. Plastic deformation was dominated by <a> basal slip, with an increasing contribution of <c+a> pyramidal II slip at higher strain levels, particularly in grains that had already activated basal slip. Twinning played a negligible role, and grain boundary sliding was suppressed due to the continuous eutectic phase at the grain boundaries. Schmid factor analysis confirmed that both <a> and <c+a> slip systems followed the Schmid law. Large lattice misorientations developed in the grains, leading to a rapid increase in the density of geometrically necessary dislocations, which triggered dynamic recrystallization at low strains (6.5%). Dynamic recrystallization, driven by progressive lattice rotation and grain fragmentation, hindered the strain hardening. Fracture occurred at low strains (< 10%) and was triggered by the presence of oxide particles that acted as crack initiation sites. These findings provide insights into the deformation behavior of additively manufactured Zn-based alloys and provide valuable guidance for the development of next-generation biodegradable Zn implants with enhanced mechanical performance.