Star‐Shaped Crystallographic Cracking of Localized Nanoporous Defects

Abstract

On self-assembled monolayer-covered Cu-Au substrates, localized volume shrinkage at initial dealloying sites leads to cracks within the attacked regions. It is started from well-controlled surface structures to gain fundamental insights in the driving mechanisms of localized corrosion and crack formation. Both the crack density and the crack morphology are critically dependent on surface orientation, crystallography, and inhibitor molecule species.

Stress Corrosion Cracking Resistance of Cold-Sprayed Al 6061 Deposits Using a Newly Developed Test Fixture

“…In the wrought sample strained to 25% yield (Figure 16a), although few fine dimples exist, the fractography predominately shows intergranular fracture; Figure 16b shows the grain boundaries have been attacked. This type of failure is caused by elemental depletion at the grain boundary or weakening of the grain boundaries from oxidation, chemical attack, or embrittlement [17,27,[46][47]. Figure 17a,b also shows additional transgranular fracture.…”

“…Various studies have also shown that the stress corrosion cracking behavior of aluminum alloys in chloride environments is largely dependent on the specific immersion conditions [18,19,[44][45][46]. Additionally, precipitates can cause areas of localized corrosion because of differences in corrosion potential as compared with surrounding areas, resulting in hydrogen evolution, promoting SCC [7][8][9][10]17,[48][49]. The build-up of hydrogen can eventually embrittle the material and cause cracking [11][12][13].…”

“…As a low-temperature process, it operates below the melting point of metals and results in very low porosity deposits without the need for combustible gasses. Additional motivation to use this process is the low oxide content, which can improve corrosion resistance, mechanical properties, and wear resistance by eliminating sites for localized corrosion and premature failure.There has been a great deal of research into corrosion mechanisms in metallic materials over the past century [5][6][7][8][9][10][11][12][13][14][15][16][17]. Atmospheric or environmentally assisted corrosion is one of the least understood areas of corrosion.…”

“…Dealloying is associated with stress corrosion cracking in aluminum alloys, steels, and noble metal alloys such as AgAu and CuAu [14][15][16]. Renner et al [17] noted that cracks can form in CuAu alloys during local dealloying and depend on the crystallographic orientation of the substrate material and stability of applied inhibitor layers.Higher strength alloys such as the 7xxx and the 2xxx alloys are more susceptible to SCC [18][19][20][21][22] due to the high alloying additions. The 6xxx series alloys are usually not as susceptible to SCC when exposed to high tensile stresses and highly corrosive atmospheres [18,[21][22][23].…”

“…Dealloying is associated with stress corrosion cracking in aluminum alloys, steels, and noble metal alloys such as AgAu and CuAu [14][15][16]. Renner et al [17] noted that cracks can form in CuAu alloys during local dealloying and depend on the crystallographic orientation of the substrate material and stability of applied inhibitor layers.…”