A high-strength AlZnMg alloy hardened by the T-phase precipitates

Highlights: • The presented alloy has better strength and corrosion resistance than that of the 7150 Al alloy. • The presented alloy is strengthened by T-phase precipitates rather than η-type phases. • Most of the grain boundary precipitates in the alloy are of T-phase rather than η-phase. • The T-phase precipitates are spherical-like in their early-stage and polyhedral-like in late-stage. - Abstract: An Al–7.60Zn–2.55Mg (wt.%) alloy with a characteristically high Mg-to-Zn atomic ratio has been investigated for its strength and hardening precipitates in comparison with that of 7150 alloy. It is shown that this alloy yields a rather high strength upon thermal ageing. Interesting is that this high-strength alloy is hardened by the coherent polyhedral T-phase [(AlZn)₄₉Mg₃₂] particles and their early-stage precipitates, which is very different from that of other high-strength AA7xxx AlZnMg(Cu) alloys hardened by the disc-like precipitates of the η-type phases