| Magnesium alloy is an excellent light structural metal with favorable mechanical properties,damping performance,biocompatibility,electromagnetic shielding and so on.But conventional magnesium alloy has poor corrosion resistance,which limits its application greatly.The phytic acid surface treatments is a new method for magnesium alloy and it can not only coordinate with magnesium alloy matrix to produce compact coating,but also react with organic coating to improve the interfacial adhesion.Fiber mental laminates,represented by glass fiber reinforced aluminium laminates,has prominent damage tolerance,corrosion resistance,fire resistance,light quality and so on,which has been widely applied in aircraft envelope.Glass fiber reinforced magnesium alloy laminates,as a new kind of fiber mental laminates,has excellent integrated properties and its lightweight effect is better than that of GLARE.This paper develop new methods on how to combine magnesium alloy and glass fiber reinforced resin firmly.The phytic acid treatments and preparation of glass fiber reinforced magnesium alloy laminates were studied emphatically,which aims to develop new material for glass fiber reinforced magnesium laminates and new anticorrosion technology for magnesium alloys.The main work and achievements are as follows:(1)Processing parameters of phytic acid treatments and performance of magnesium alloy surface were studied.The optimal process parameters of phytic acid treatments were obtained by experiments,which is under the condition of pH=4.5 at 30?for 30min.In that condition,reaction processing is intense and the phytic acid conversion coating is complete,uniform thickness,compact and smooth.The EDS results indicate that the main elements of phytic acid conversion coating are Mg?C?O?Al?P and so on.The atom percentage of Mg is as high as 30%,which demonstrates that phytic acid and the matrix have sufficient chemical and chelate reaction.The surface properties of magnesium alloy with phytic acid treatments were tested and evaluated by dynamic contact angle tester.The dynamic contact angle of magnesium plate with phytic acid treatments in epoxy resin reaches minimum value at57.8°,which is 18.7°lower than that of magnesium alloy with 1000#sandpaper treatments.Besides,the surface energy and polarity component of corresponding magnesium plates with phytic acid treatments are 142.30 mN/m and 141.12 mN/m respectively,which are 2.76 times and 2.97 times higher than of the magnesium plates with sandpaper treatments.(2)The“3+2”magnesium alloy laminates(3 layers of magnesium alloy plates+2 layers of glass fiber)and“1+2”magnesium alloy laminates(1 layer magnesium alloy plate+2 layers of glass fiber)were prepared by hot pressing method.(3)The mechanical properties of“3+2”magnesium alloy laminates were analyzed as shown.The tensile tests show that the maximum tensile strength of“3+2”magnesium alloy laminates treated with sandpaper and phytic acid reached 283MPa and 244MPa,and the modulus of elasticity are 51GPa and 47GPa,respectively.After monolayer's failure,the retention rate of tensile strength were 74.2%and 69.7%,indicating that“3+2”magnesium alloy laminates with phytic acid treatments were more resistant to the whole structure failure.Bending tests on“3+2”magnesium alloy laminates show that“3+2”magnesium alloy laminates with phytic acid treatments is relatively difficult to crack.And the cracking size between plates is smaller than that of“3+2”magnesium alloy laminates with sandpaper treatments,which shows that the bonding strength enhanced distinctly.The maximum load,bending strength and bending modulus are 0.446KN,200MPa and 35GPa respectively,which are better than that of“3+2”magnesium alloy laminates with sandpaper treatments.(4)The corrosion resistance of“1+2”magnesium alloy laminates were tested and analyzed.The corrosion potential of magnesium alloy treated with phytic acid is-1.28V,which moved forward than that with sandpaper.And the corrosion current density of the magnesium alloy with phytic acid decreases from 251?A/cm~2 to 158?A/cm~2 compared to that with sandpaper.The corrosion potential of“1+2”magnesium laminates with phytic acid and sandpaper are-0.30V and-0.33V,which move forward 1.05V and 0.98V.In addition,corrosion current density of that are 0.245?A/cm~2 and 0.316?A/cm~2,respectively.The corrosion rate decreases by 3 orders of magnitude,which shows that the corrosion resistance of magnesium alloys is significantly improved.According to the analysis of hydrogen evolution tests,the hydrogen volume per unit area of magnesium alloy plates with phytic acid treatments decreased significantly.The hydrogen volume per unit area of magnesium alloys with phytic acid treatments at12h and 24h are 0.419 ml/cm~2 and 1.29 ml/cm~2,which are 34.1%and 53.5%of that with sandpaper treatments.The hydrogen volume per unit area of“1+2”magnesium alloy laminates treated with phytic acid and sandpaper at 24h are 0.040 ml/cm~2 and 0.046 ml/cm~2,which are 3.1%and 1.9%of corresponding magnesium alloys,showing excellent corrosion resistance.The immersion experiments of“1+2”magnesium alloy laminates were tested.After 48h immersion,the corrosion of magnesium treated with sandpaper covered the whole surface area,while the magnesium alloy treated with phytic acid treatments didn't expand about 1/3 surface area until 48h.After 240h immersion,partial glass fiber of“1+2”magnesium alloy laminates with sandpaper treatments peeled off from matrix with slight corrosion,but glass fiber of“1+2”magnesium laminates with phytic acid treatments didn't peel off and the appearance had no significant changes,showing outstanding corrosion resistance. |
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