Study On Microstructure Evolution And Corrosion Resistant Properties Of AZ91Magnesium Alloy At High Strain Rates

Magnesium alloy has been widely applied in aviation, aerospace, automobile andso on, for its nice properties of low destiny, high specific strength and goodrecoverability, however, the bad corrosion resistance has always restricted itsapplication. In this article, the microstructure evolution and corrosion resistance ofAZ91Magnesium alloy was studied under the condition of high strain rates by SHPBand LSP techniques in which way the research range of Magnesium alloy was widenedand a great theoretical and practical significance was made at the same time.The solution and aging treatment on cast AZ91Magnesium alloy were made firstand the relevant micro-structure, mechanical properties and corrosion resistance wereobserved, too. After the above process, the AZ91Magnesium alloy of as-cast and agingstate were impacted separately by SHPB and then the related micro-structure,mechanical properties, deformation mechanism and corrosion resistance were studied.The results showed that after SHPB, the grain of Magnesium alloy were refined and withthe increasing of strain rates and the microhardness of the alloy was improved. Themicrohardness of cast AZ91magnesium alloy is130HV and the solid solution age-treatment is150HV at the high stain rates of2500s-1, the thickness of the deformationlayer was about100μm. After SHPB, the corrosion potential moved to a positivedirection and as the strain rate become higher, the ampere density was reduced and theresistance of the electrochemical reaction was increased significantly, the declinedcorrosion current density was caused by the slow electronic migration rate and the ratethat the conductive ions moved through the passive film.The specimen after aging treatment were impacted separately by one time andthree times’ LSP, the results showed that the self-corrosion potential of the specimenmoved remarkably to the positive direction after one time’s LSP, it was about810mVhigher than the untreated specimen and that potential after three time’s LSP was380 mV higher as well than the one time’s LSP, the corrosion resistance increased notably.After one time and three times’ LSP, the residual compressive stress were respectivelyimproved to-124MPa and-156MPa, the surface hardness was reached to120HV and150HV, and the grain were refined to the size of100nm~200nm.The surface residualcompressive stress made the magnesium alloy surface “broken cavity” and “unbrokencavity”, grain refinement made the magnesium alloy surface uniform corrosion.