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Influence of Exposure Time on Tensile Behavior The determined tensile property degradation occurs gradually. It is shown in Figs. 9.14- 9.17; they display the trends of property decrease versus the exposure time into exfoliation corrosion solution for the alloys 2024, 6013, 8090, and 2091, respectively. For the alloy 2024 the gradual property degradation with exposure time was determined for atmospheric corrosion tests as well Fig. 9.18. As seen in these figures all properties are decreasing nonlinearly with the exposure time. By defining with P(t) = [AP(i)/Pinitial x 102] the loss in percent of the respective property during the exposure, the results of Figs. 9.14- 9.17 were used to formulate expressions of the gradual decrease of the material properties. Applied functions as well as the values of the respective fitting parameters used for the case of exposure in exfoliation corrosion solution are summarized in Table 9.40. For atmospheric corrosion, exposure duration is still too short to formulate reliable functions. The yield and ultimate stress drop during exfoliation corrosion exposure are best approximated by applying power time functions. The power exponents were found for all alloys <1, that is, the obtained property loss occurs with a decreasing rate. The reported behavior is consistent with the experimental observation of the progressive growth of a protective oxide film on the materials surface [74]. The growth of this film has been found to follow power time functions; the rate of attack during exposure decreases at very low rates or it ceases. The drop of elongation to failure and

Immersion Corrosion Corrosion

Immersion Corrosion Corrosion

Immersion Corrosion Corrosion

FIGURE 9.11 Tensile behavior of alloy 6013 following corrosion exposure according to relevant specifications for accelerated corrosion tests: (a ) L direction and (b) LT direction.

Immersion Corrosion Corrosion

FIGURE 9.11 Tensile behavior of alloy 6013 following corrosion exposure according to relevant specifications for accelerated corrosion tests: (a ) L direction and (b) LT direction.

energy density were fitted well by exponential time functions. In the equations for tensile ductility degradation, A50( /> and W f stand for the final value of the respective property loss. Hence, they may be interpreted to reflect the susceptibility of the property to the corrosive environment. The parameters P and k indicate the rate of property decrease in the corrosive solution. The exponential form of these

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

FIGURE 9.12 Tensile behavior of alloy 8090 following corrosion exposure according to relevant specifications for accelerated corrosion tests: (a) L direction and (b) LT direction.

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

Reference Intergranular Alternate Salt Spray Cyclic Exfoliation Exfoliation Outdoor Immersion Acidified Corrosion Corrosion Exposure

FIGURE 9.13 Tensile behavior of alloy 2091 following corrosion exposure according to relevant specifications for accelerated corrosion tests: (a) L direction and (b) LT direction.

equations leads to the association of diffusion-controlled processes. In addition, the occurrence of saturation values for the tensile ductility degradation is supporting the viewpoint of a volumetric, diffusion-controlled phenomenon. In [60] evaluation of exfoliation corrosion tests performed on 2024-T351 specimens has shown a good correlation between hydrogen evolution and the available surface

Reference Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Corrosion Corrosion Corrosion Corrosion Corrosion Corrosion

Reference Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Corrosion Corrosion Corrosion Corrosion Corrosion Corrosion

Reference Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Corrosion Corrosion Corrosion Corrosion Corrosion Corrosion

Reference Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Exfoliation Corrosion Corrosion Corrosion Corrosion Corrosion Corrosion

FIGURE 9.14 Gradual tensile property degradation for alloy 2024 during exposure in exfoliation corrosion solution: (a) L direction and (b) LT direction.

area for penetration. Indirect evidence was reported that hydrogen was initially absorbed chemically. Recall also present results of corrosion characterization; increasing pitting density and occurrence of intergranular attack when exposure time increases were reported. Referred results provide substantial explanations in favor of hydrogen absorption and bulk penetration.

Ultimate Stress

Yield Stress

Elongation to failure

Energy density

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