Spherical strengthening precipitate in a Mg-10 wt%Y alloy with superhigh pressure aging

A Mg-10 wt% Y alloy exhibited age hardening response by both artificial aging at 220 °C (T6) and superhigh pressure aging (6 GPa) at 300 °C (SHP-300). A spherical strengthening precipitate (Mg24Y5) was achieved after SHP-300 heat treatment, which was different from conventional plate-shaped strengthening precipitate (β′) after T6 treatment. Compared with the T6 state sample, the peak hardness, strength and ductility were improved by means of SHP-300 treatment. The improved hardness and strength were associated with the nano-scale precipitate (Mg24Y5) and strain hardening. The large elongation was ascribed to the formation of spherical precipitate, which can effectively reduce the stress concentration during the deformation process.

► Age hardening behavior is found in Mg-10Y alloy with superhigh pressure aging.
► A spherical precipitate is achieved in Mg-10Y alloy by superhigh pressure aging.
► Both peak hardness and strength are improved after superhigh pressure treatment.
► High ductility is maintained due to the formation of spherical precipitate.