Mechanical degradation due to vacancies produced by grain boundary corrosion of steel
Mechanical degradation due to vacancies produced by grain boundary corrosion of steel
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DOI：
10.1016/j.actamat.2020.08.080
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发表时间：
2020-11
期刊：
影响因子：
9.4
通讯作者：
Denizhan Yavas;T. Phan;Liming Xiong;K. Hebert;A. Bastawros
中科院分区：
文献类型：
--
作者：
Denizhan Yavas;T. Phan;Liming Xiong;K. Hebert;A. Bastawros
韧性合金在腐蚀性环境中会因晶间应力腐蚀开裂而失效，这是通过机械和化学过程之间的相互作用实现的，目前尚不清楚。我们调查的低合金管线钢的晶界腐蚀产生的金属缺陷的形成和机械效果，在高敏感性的条件下，在没有析氢的应力腐蚀开裂。纳米压痕测量结果表明，局部软化腐蚀晶界附近，显着降低临界负荷位错成核。大块铁的纳米压痕的分子动力学模拟表明，金属空位，而不是间隙氢原子解释所观察到的临界载荷降低。位错激活体积和位错激活能的空位充电的样品被发现是近一半的氢充电的样品。定量协议与实验测得的压痕响应被发现为相当于在钢中的体硅浓度的空位浓度，这表明空位起源于晶界处的反应性硅溶质原子的氧化。这一结果有助于解释空位缺陷形成的化学机制，空位缺陷可能参与在没有氢脆环境下的晶界退化。
Ductile alloys fail in corrosive environments by intergranular stress corrosion cracking, through interactions between mechanical and chemical processes that are not yet understood. We investigate formation and mechanical effects of metal defects produced by grain boundary corrosion of low-alloy pipeline steel, at conditions of high susceptibility to stress corrosion cracking in the absence of hydrogen evolution. Nanoindentation measurements show local softening near corroded grain boundaries, indicated by significantly reduced critical loads for dislocation nucleation. Molecular dynamics simulations of nanoindentation of bulk iron showed that metal vacancies and not interstitial hydrogen atoms explain the observed critical load reduction. Both the dislocation activation volume and dislocation activation energy for vacancy-charged samples are found to be nearly one-half of that for a hydrogen charged samples. Quantitative agreement with experimentally measured indentation response was found for vacancy concentrations equivalent to the bulk silicon concentration in the steel, suggesting that vacancies originate from oxidation of reactive silicon solute atoms at grain boundaries. The results help explain the chemical mechanism of formation of vacancy defects that may participate in grain boundary degradation in the absence of hydrogen embrittlement environment.