Effect of multi-element synergistic addition on the microstructure evolution and performance enhancement of laser cladded Al-Mg-Zn-(Mn-Cu-Er-Zr) alloy

To satisfy the requirements of formability, strength-toughness, and corrosion resistance for laser additive manufacturing of lightweight aluminum alloy brake discs, this study adopted a thermodynamic design method incorporating Mn, Cu, Er, and Zr elements to develop multi-element Al-Mg-Zn-(Mn-Cu-Er-Zr) alloy. The optimized laser cladding process was employed to prepare a novel alloy sample. The results indicate that a novel T-AlMgZnCuZrEr phase with a distinct structure compared to the conventional T-phase in Al-Mg-Zn alloys was observed in the sample prepared by synergistic addition of Mn, Cu, Er, and Zr. Owing to the significant strengthening and toughening effects of the novel T-phase, the compressive strength and toughness product, along with the corrosion potential of the laser cladded sample reached 26520 MPa2 m1/2 and -0.73 V, respectively, which were 27% and 39% higher than those of Al-Mg-Zn alloy. The precipitation and growth mechanism of the novel T-phase was elaborated, and the kinetic equation for the in-situ precipitation of the Tphase was established. A multi-component design method for strengthening and toughening Al alloy to improve the performance by controlling microstructure through laser cladding was obtained, which provides a valuable reference for laser cladding to prepare lightweight aluminum alloy with high strength-toughness and corrosion resistance.