Achieving strength-ductility synergistic improvement in Mg alloy via non-uniform precipitate-induced nanoscale-microzone heterostructure

Nano-precipitate-strengthening often sacrifices ductility in Mg alloys. Herein, we report a novel nanoscale-microzone heterostructure that can yield strength-ductility synergistic improvement. The nanoscale-microzone heterostructure unit is composed of the soft zone with slender sheet-like precipitates along dislocation lines and the hard zone with β’ precipitate arrays on dislocation loops/arrays. The Mg-9.9Gd-0.25Ag-0.19Zr alloy with nanoscale-microzone heterostructure achieves ultra-high strength (YS: 441 MPa, UTS: 475 MPa) and improved uniform elongation (UEl: 6.0%, 7.5 times that before aging treatment). This mechanism based on nanoscale-microzone heterostructure is expected to provide a feasible avenue to develop precipitation-strengthened Mg-RE alloys with ultra-high strength and acceptable elongation.