Excellent mechanical properties of a ZrTi-based alloy via laser surface remelting

•Laser surface remelted ZrTi45Al15 (at.%) alloy possesses gradient microstructure.•Ultra-high strength of 1550 MPa and good tensile elongation of 10.3% are obtained.•Deformation depends on the synergistic effect of various deformation mechanisms. In recent years, more and more attention has been paid to the research and development of high strength Zirconium-Titanium (ZrTi) based alloy system. However, like almost all metallic materials, increasing the strength of ZrTi alloy leads to a significant decrease in plasticity. In this paper, high strength and toughness ZrTi alloy with gradient structure was prepared by laser surface remelting. The metastable β phase with high dislocation density was obtained by laser local heating and rapid cooling, and a large amount of acicular martensite structure was formed in the heat affected zone, combined with the dual phase of the matrix, a gradient structure was formed from the surface to the matrix. The tensile strength was increased to 1550 MPa and the tensile elongation was kept above 10%. The composite deformation mechanisms of dislocation slip, twinning and stress-induced martensitic transformation of gradient structure have also been discussed.