Quantum chemical molecular dynamics study of stress corrosion cracking behavior for fcc Fe and Fe–Cr surfaces
Quantum chemical molecular dynamics study of stress corrosion cracking behavior for fcc Fe and Fe–Cr surfaces
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DOI：
10.1016/j.corsci.2008.01.032
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发表时间：
2008-06
影响因子：
8.3
通讯作者：
N. Das;Ken Suzuki;Y. Takeda;K. Ogawa;T. Shoji
中科院分区：
文献类型：
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作者：
N. Das;Ken Suzuki;Y. Takeda;K. Ogawa;T. Shoji
采用量子化学分子动力学模拟方法，研究了Fe(111)和Fe-Cr(111)裸表面在高温水中的应变氧化行为。模拟结果表明，由于氧和铬原子之间的强键作用，Fe和Fe-Cr的表面形貌有所不同。氧原子被捕获在Fe-Cr表面的铬原子周围，而氧则穿透到Fe裸露表面的晶格中。结果表明，氧在Fe-Cr晶体表面的扩散率降低。结果表明，在氧化过程开始时，铬在Fe-Cr清洁表面发生优先氧化。当应变作用于缺陷表面时，氢和氧的扩散显著增加。金属晶格中的氢原子具有高度的负电荷，这表明表面被H负电荷氧化。带负电荷的氧原子与金属原子发生键合，破坏了金属-金属的最终成键。这些键的断裂表明在表面形成了氧化层，并在随后的局部腐蚀形核(如应力腐蚀破裂)中起到了关键作用。
Quantum chemical molecular dynamics simulation was applied to study the oxidation of bare Fe (111) and Fe–Cr (111) surfaces with strain in high temperature water. Simulation results implied the surface morphologies differ from Fe to Fe–Cr because of strong bond between oxygen and chromium atoms. Oxygen atoms were trapped around chromium atoms at Fe–Cr surface, whereas oxygen penetrated into the lattice of Fe bare surface. As a result, the oxygen diffusivity into the Fe–Cr crystal surface reduced. It indicated that the preferential oxidation of chromium would take place on Fe–Cr clean surface at the beginning of the oxidation process. Diffusion of hydrogen and oxygen significantly increased when strain applied to the defective surface. Hydrogen atoms being in the lattice of metal possessed the highly negative charge which indicated the surface oxidized by this negative charge H. Negative charged oxygen atoms make bond with the metallic atom which breakage ultimate metal–metal bond. These bond breakages indicated the formation of oxide layer on the surface and play a key role in subsequent localized corrosion nucleation like stress corrosion cracking.