通过晶界工程 (GBE)处理, 可使304不锈钢样品中的低ΣCSL晶界比例提高到70%(Palumbo-Aust标准)以上 , 同时形成了大尺寸的“互有Σ3$n取向关系晶粒的团簇”显微组织. 采用C型环样品恒定加载方法, 在pH值为2.0的沸腾20%NaCl酸化溶液中进行应力腐蚀实验. GBE样品在平均浸泡472 h后出现应力腐蚀裂纹, SEM, EBSD和OM分析表明, 应力腐蚀开裂(SCC)为沿晶开裂(IGSCC)和穿晶开裂(TGSCC)的混合型. 而未经GBE处理的样品在平均浸泡192 h后出现多条应力腐蚀主裂纹, 且多为沿晶界裂纹. 经过GBE处理的样品中大尺寸的晶粒团簇及大量相互连接的Σ3-Σ3-Σ9和 Σ3-Σ9-Σ27等Σ3n类型的三叉界角, 阻碍了IGSCC裂纹的扩展, 从而提高了304不锈钢样品的抗IGSCC性能.
The grain boundary network in a 304 stainless steel can be controlled by grain boundary engineering (GBE). The total length proportion of Σ3n coincidence site lattice (CSL) boundaries was increased to more than 70%, and the large size highly twinned grain-cluster microstructure formed through the treatment of GBE. Stress corrosion cracking (SCC) susceptibility of 304 stainless steel was evaluated through C-ring specimen tests conducted in acidified boiling 20%NaCl solution. Based on the characterization by SEM, EBSD and OM, it was found that the large grain-clusters associated with many interconnected Σ3-Σ3-Σ9 and Σ3-Σ9-Σ27 triple junctions produced by GBE arrest the IGSCC cracks and improve the resistance to IGSCC.
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