Dislocation arrays, precipitate bands and free zones in forged Mg-Gd-Y-Zr alloy

Dislocation arrays are extensively generated in the hammer forged and then annealed Mg-8.3 Gd-2.6 Y-0.4 Zr (wt. %) alloy. Microscopy characterizations reveal a high thermal stability of these dislocation arrays. During ageing treatment, dislocation arrays act as preferred sites for precipitation of β' phase, promoting the formation of the bamboo-like precipitate bands, and resulting in a depletion of solutes nearby and the formation of precipitate free zones (PFZs) along these bands. The forged samples after annealing and then ageing at an optimized temperature of 265 °C for different periods exhibit a similar strength and strain hardening but an increased elongation with ageing time, suggesting that the precipitate bands act as strong barriers for the motion of dislocations and twins while PFZs can effectively enhance deformability of Mg-Gd-Y-Zr alloy.