Anomalous high-temperature strength-ductility synergy for Mg-Gd-Y-Zr alloy via wire-arc directed energy deposition

This study investigates the Mg-6Gd-3Y-0.4Zr alloy fabricated via wire-arc directed energy deposition (WA-DED) to achieve exceptional high-temperature strength-ductility synergy. The microstructure, elemental distribution, and mechanical properties of the WA-DED alloy were systematically analyzed. Results reveal a refined equiaxed grain structure (average grain size: 21.56 μm) with Mg 24 (Gd,Y) 5 and Mg 3 Gd precipitates along grain boundaries. Remarkably, the alloy exhibits unexpected strength retention at 200°C, with ultimate tensile strength (255 MPa) and yield strength (164 MPa) comparable to room-temperature values, while elongation increases by 97% (up to 33.1%). Such a property anomaly is attributed to twin-induced dislocation pinning, which compensates for precipitate dissolution at elevated temperatures. Enhanced ductility arises from vacancy-assisted dislocation climb, matrix softening, and activation of additional slip systems. The fracture analysis confirms ductile failure with deeper dimples at high temperatures, aligning with elongation improvements. The findings demonstrate WA-DED-processed Mg-Gd-Y-Zr alloys as promising candidates for aerospace heat-resistant components.