Composition design of a novel Ti-6Mo-3.5Cr-1Zr alloy with high-strength and ultrahigh-ductility

•A novel titanium alloy with high strength and ultrahigh ductility was designed to break through the longstanding strength-ductility trade-off.•The strong strain partitioning effect and the dislocation pile-up effect caused by SIω were found and quantitatively analyzed by in situ EBSD/DIC and in situ TEM tests, respectively.•The TRIP/TWIP/DPU coupling effect during plastic deformation was firstly proposed and deciphered.