Research On Rolling Technology, Microstructure And Mechanical Properties Of ZK Magnesium Alloys

During the recent years, energy and environmental problems have attracted moreand more attention. As the lightest metallic structural materials, magnesium and itsalloys are receiving unprecedented attention. Especially, wrought magnesium alloyplates have broad application prospects in the aviation aerospace, automotive,3C dueto their low density, high specific intensity and rigidity. However, the rollingprocessing of magnesium alloy plates is very difficult because of the intrinsicclose-packed hexagonal crystal structure. At present, the rolling technologyconcerning magnesium alloys especially in ZK series are still scarce. In this paper,with resolving rolling problems as the purpose, casting-solid solution-rolling as theclues, ZK21and ZK40magnesium alloys as the research object, the effects ofsolution treatment and rolling parameters on the microstructure and mechanicalproperties of the plates are investigated adopting microstructures observing andmechanical properties measurement methods. The results show that:(1) A large number of precipitated phases exist alone grain boundary in cast ZKseries magnesium alloy, which seriously worsens the rolling properties. Solutiontreatment can promote the dissolution of precipitated phases and improve the rollingproperties. Under the conditions of320~340℃and1~3h, the precipitated phases aredissolved and the hardness increase gradually with increasing the solution treatmenttime. The optimized solution treatment technology is320℃and3h.(2) Under the lower pass reduction conditions, the main deformation mechanismis twining with lenticular shapes tensile twins produced firstly. With the increasingreduction in each pass, thin and straight of compression twins gradually become themain twining mode combining with the second twins. Once the pass reduction is largeenough, dynamic recrystallization take place especially in grain boundaries, twinboundaries and trigeminal grain boundaries, and dynamic recrystallization grainsexpand to grain interior with the creasing of pass reduction. Improving temperature ishelpful for the compression twins in lower pass reduction and dynamicrecrystallization in higher pass reduction.(3) The hardness increases with the increasing of pass reduction in both alloys.During the hot rolling process, the density and interaction of twins also increaseincreases with the increasing of pass reduction and leads to working hardening, being responsible for the increase of hardness.(4) Considering the plate rolling forming properties and the extent of grainrefinement and material hardness, preliminary determine the rolling process of ZK21magnesium alloy as: solution temperature320℃, holding time3h, rollingtemperature340℃, pass reduction55%; rolling process of ZK40magnesium alloy as:solution temperature320℃, holding time3h, rolling temperature340℃, reductionin pass50.8%.