Research On Microstructure And Mechanical Properties Of ZK60Magnesium Alloy Processed By Electropulsing Treatment

Recently, magnesium alloys are widely used in industries due to thelow density and high specific strength. Microstructure optimizing and grainrefinement are being the hotspots in academia gradually. Grain refinement isconsidered to be one of the most efficient ways to improve both strength andplasticity of magnesium alloys.The current paper investigated the influences of electropulsingtreatment (EPT) on microstructure, mechanical properties and staticrecrystallization (SRX) behavior of the rolled ZK60magnesium alloy sheets.Firstly, the ZK60alloy sheets with high densities of dislocation werefabricated by rolling process. Secondly, the different states of recrystallizedmicrostructures were obtained by EPT with different electropulsing parameters.Finally, the microstructure, mechanical properties and static recrystallization(SRX) behavior of the rolled ZK60magnesium alloy sheets during EPT wereinvestigated.The experimental results indicated that the SRX of the rolled ZK60 alloy sheets processed by EPT was liable to occur compared with that processedby routine heat treatment (RHT). Furthermore, the recrystallizationmicrostructure was refined and the comprehensive mechanical properties wereimproved tremendously by22μs-10min-100Hz EPT. The grain size was refinedfrom100μm to2μm, the tensile stress of ZK60alloy sheets was improved from210MPa to320MPa and the tensile elongation was increased from14.6%to30%. Analyses on measured temperature and theoretical calculation of Fourierheat transfer model were carried out to discuss the effect of Joule heat inducedby EPT on recrystallization behavior. When the electropulsing passes throughmetal materials, the system free energy of the metal materials will obtain anadditional term Gein comparison with the system without electropulsing underthe same state, and this additional energy is directly proportional to the electricresistance of metal materials. The two different states of ZK60alloy beforerecrystallization and after recrystallization led to the different Gibbs increment.The difference between two Gibbs increments increases the driving force ofrecrystallization. Moreover, the SRX mechanism under EPT was studied basedon subgrain coalescence theory. EPT accelerated the nucleation of strain-freegrains by subgrain coalescence mechanism.