Abstract
The development of high-performance magnesium (Mg) alloys requires precise microstructural control through composition design and thermomechanical processing. While yttrium (Y) addition is known to benefit Mg alloys, its role in dynamic recrystallisation (DRX) mechanisms and the resulted synergy of mechanical and corrosion properties within the Mg-Zn-Al-Mn system remains elusive, especially when integrated with solution treatment and extrusion. In this work a systematic investigation is performed to study the effect of Y content (0−5.0 wt.%) on the solution-treated and extruded Mg-2.0Zn-2.0Al-0.3Mn alloy. The dominant process of DRX from twin-induced DRX (TDRX) at 0 % Y gradually transits to discontinuous and continuous DRX (DDRX, CDRX), particle-stimulated nucleation (PSN), and the Smith-Zener pinning effect in Y-containing alloys. This transition is driven by the formation of Al₂Y and (Al, Zn)₁₁Y₃ precipitates and leads to continuous grain refinement and twin suppression. An optimized Y content is identified at 3.0 wt.% to reach a strength- plasticity ultimate tensile strength of 289.4 MPa, yield strength of 214.1 MPa and elongation of 25.8 % along with the best corrosion resistance.

Key words
magnesium alloy, microstructures, mechanical properties, corrosion resistance

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