Effect of a compound modification process on the microstructure and mechanical properties of ZK60 magnesium alloys

ZK60 magnesium alloy was compound treated by combining rolling and ultrasonic surface rolling processing (USRP). The result showed that the gradient nanostructure (the grain size change with a gradient variation from nanometer scale to micrometer scale, from the top surface to bulk) prepared by USRP in the magnesium alloy improved the strength of the alloy while maintaining enough plasticity because the sharp decline in the plasticity was delayed by the highly uniform elongation (UEL) of the gradient structure. Meanwhile, after compound modification, the tensile results showed that the yield strength (YS) and ultimate tensile strength (UTS) of the ZK60 alloy were improved from 130 MPa and 243 MPa to 283 MPa and 359 MPa, respectively, and the strength plasticity product was increased from 4106.7 to 5313.2. The improvement of strength was determined by the combined effects of fine grain strengthening, dislocation strengthening and precipitation strengthening. Combine the analysis of the above results, it could be concluded that the compound modification process achieved an unexpected effect in the ZK60 magnesium alloy, which will inspire other magnesium alloy researchers.