Research On The Effect Of Pre-deformation On Mechanical And Corrosion Properties Of Precipitation-strengthened Magnesium Alloys

Magnesium alloy is an ideal choice to realize the lightweight of metal structure materials due to its low density,high specific strength and so on.However,the wide application of magnesium alloys is limited due to its disadvantages such as poor formability at room temperature,low absolute strength and poor corrosion resistance.Precipitation-strengthened magnesium alloys usually have better properties.And predeformation treatment before aging is an important method to improve precipitation hardening behavior,because it can produce dislocations and twins which can refine the microstructure and ameliorate the morphology and distribution of precipitates,and then regulate the strength and corrosion resistance of precipitation-strengthened magnesium alloy.In this paper,aiming to induce twins and dislocations in the precipitationstrengthened alloys,the pre-deformation processes including rolling and triaxial compression were applied in the solid-solutioned AZ80 and ZK60 hot-rolled plates.The evolutions of microstructure were investigated by using the modern microscopic analysis and characterization methods,mechanical properties testing,hydrogen evolution and electrochemical testing.Meanwhile,the synergic effects of pre-deformation and aging on the mechanical and corrosion properties were discussed in detail by means of mechanical properties testing,hydrogen evolution and electrochemical testing.The main results are as follows:(1)Both dislocations and twins were successfully produced in the solid-solutioned AZ80 alloy by rolling.The number of twins increased with the increase of rolling strain.The morphologies of precipitates in the solid-solutioned samples after aging were lamellar,and the precipitates in the pre-deformed samples after aging were plate shape.With the increase of rolling deformation,the precipitated second phases after aging get a more uniform distribution.Rolling deformation significantly improved the compressive and tensile strength of AZ80 alloy after aging,and effectively improved the tensioncompression yield asymmetry,as well as its corrosion resistance.When the deformation was up to 12%,the strength and corrosion resistance of AZ80 alloy showed the best performances.(2)The triaxial compression pre-deformation also introduced a large number of twin structures and dislocations into the solid-solutioned AZ80 alloy,which also changed the morphology and distribution of the second phase.The precipitated phase of the predeformed samples after aging were plate shape.Both the corrosion resistance and the strength of AZ80 alloy after aging were improved significantly by triaxial compression pre-deformation,and the corrosion resistance and strength of AZ80 alloy was improved with the increase of compression passes.(3)After triaxial compression deformation,a large amount of twins and dislocations were formed in the solid-solutioned ZK60 alloy,which significantly improved the compressive yield strength of AZ80 alloy after aging,and effectively improved the tension-compression yield asymmetry,as well as its corrosion resistance.The strength and corrosion resistance increased with the increase of compression passes.The number of twins was significantly affected by the grain size and the strain level of deformation.The solid-solutioned samples possessed the largest grain size after solution treatment at480 ℃/2 h + 510 ℃/24 h + water quenching,and they had the largest number of twins after 12 passes compression.The morphologies of precipitates were both rod-shaped and disk-shaped in the direct aging and pre-deformed aging of the solid-solutioned samples.However,the number of rod-shaped precipitates in the pre-deformed aging samples was significantly reduced,and the disk-shaped precipitates were distributed along the twin boundaries.