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<p>Hydride to promote alloy fracture. The proposed mechanism of hydrogen induced cracking are mainly the following theory: Hydrogen pressure theory: When there is supersaturation H in the metal, it will  ultradecking composite decking menards  combine into H2 in various microscopic defects, and the room temperature is irreversible reaction, namely H2 Will not be decomposed into H.</p> <p> With the increase of H2 concentration in the defect, the hydrogen pressure also increases.When the hydrogen pressure is greater than the yield strength will produce local plastic deformation, the surface uplift, the formation of hydrogen bubbles. (B) weak bond theory : Hydrogen in a metal reduces the bond strength of atoms, and when the local stress concentration is equal to the bond strength of atomic bonds, the atom bonds are broken and the microcracks nucleate. Hydrogen reduces the surface energy theory: Hydrogen reduces the bonding force while necessarily lowering the surface energy and vice  exterior wood stairs  versa Hydrogen is adsorbed on the inner surface of the metal and the surface energy is decreased, leading to a decrease in the critical stress necessary for the crack to expand unstably. This is not applicable to metallic materials because plastic deformation work is not taken into account. </p> <p> Hydrogen induced cracking: The mechanism considers the hydrogen to promote the local plastic deformation, hydrogen to reduce the atomic bonding force and hydrogen pressure. Anodic dissolution Anodic dissolution theory [7 ~ 9] that the continuous dissolution of the anode metal causes SCC crack Nuclear and expansion, resulting in the fracture of the alloy structure.Aluminum alloy SCC anodic dissolution theory of the main points are as follows: build a deck bench in existing deck  Anode Channel Theory: Corrosion along the local channels and the occurrence of cracks, tensile stress perpendicular to the channel, produced in the local crack tip Stress concentration in the aluminum alloy pre-existing anode channel caused by the grain boundary precipitates and the potential difference between the base caused by the stress is to open the crack exposed fresh surface in this case, the corrosion along  unique 24 round deck railing  the grain boundary accelerated</p>