Study On Corrosion Resistence Of Cold Rolled State5E62Contained Erbium

The strength and the resistance to corrosion are impoved by adding a smallamount of Zn in high Mg content alloys, and the comprehensive performance areeffectively modificatived by addition trace Er in alloys. In order to research theinfluence of cold deformation and heat treatment to the5E62alloys contained Zn、Er,which have five different cold deformations. The susceptibility of Intergranularcorrosion of different cold deformation alloys with different annealing state weremeasured by Nitric Acid Mass Loss Test (NAMLT), the corrosion morphology andmicrostructure of alloys with typical states were analyzed by optical microscopy(OM), measure minimum sensitization time to become susceptible to IGC orstablization time of different annealing state, build the curve of minimum sensitizationtime to become susceptible to IGC or stabliztion time for different cold deformation5E862alloys. Getting the stabilization process of55%cold deformation alloy bysensitizing heat treatment for the stabiling annealing alloy, measuring the the propertyof exfoliation corrosion of stabiling annealing state by Immersion Test. The corrosionmorphology and microstructure of alloys with typical states were analyzedtransmission electron microscopy (TEM).The relation graph of temperature and minimum sensitization time to becomesusceptible/IGC or stablization time VS deformation for5E62alloy established byNAMLT shows, the curves of minimum sensitization time to become susceptible toIGC or stabliztion time for different cold deformation5E862alloys like gradient “U”,the inner of the curve is the area of susceptible to IGC, the outside is the area ofresistance to IGC. The area of susceptible to IGC increase, and the property ofresistance to IGC is worse when the strain rise. The stabilization temperature of5E62alloy is240℃,150℃~200℃is the sensitization temperature, the resistance propertyto IGC of150℃is the worst; the;220℃~230℃is the transition temperature range.The results of NAMLT and Exfoliation Cossosion Test with differentstabilization annealing state of different cold deformation alloy shows,35%and55%cold deformation alloy have the excellent property of resistance to corrosion. Wechoose the55%cold deformation as the best deformation consider the mechanicalproperty. The stablization time of55%cold deformation alloy is5h to10h, which testby sensitization test, eventually, the stabilization process of55%cold deformation alloy is240℃×5h~10h.The TEM indicated that the second phase precipitated continuously along thegrain boundaries in200℃×2h state alloy with70%cold deformation at sensitizationstate, which lead to IGC. However, there was no continuous precipitation on the grainat completely stabilization state, which has the excellent property of resistance tocorrosion. The semicontinuous second phase observed on the grain boundaries in240℃×2h state alloy with55%cold deformation. And240℃×24h showed nice IGCproperty for only the isolated phase (β phase or τ phase) observed. The τ precipitationdispersed in the grain because of the addition of a little Zn, or may precipitationdiscontinuely on the grain boundary.