Microstructure evolution and mechanical anisotropy of AZ80-Ag magnesium alloy: Effect of isothermal semi-closed die forging and subsequent aging

A large-size AZ80-Ag magnesium alloy support beam was fabricated via isothermal semi-closed die forging (ISDF). Its microstructure features and mechanical properties with or without subsequent aging were systematically characterized. The results indicate that the ISDF at 400°C creates strong basal texture and leads to an obvious mechanical anisotropy between the height direction (HD) and transverse direction (TD). Subsequent aging at 175°C can promote the discontinuous or continuous precipitation of β-Mg17Al12 phases without changing the texture mode, whilst the mechanical anisotropy is significantly weakened as the difference in yield strength between TD and HD decreases from 71 MPa to 6 MPa after aging for 12 h. Such aging-induced anisotropy-weakening effect results from the fact that the HD is a soft direction for basal slip and the precipitate-strengthening related to β-Mg17Al12 is more significant in this direction.