PRODUCTION OF SENSITIZATION-RESISTANT MATERIALS BY TWIN-INDUCED GRAIN BOUNDARY ENGINEERING

奥氏体不锈钢中由于晶界处的碳化铬析出而引起的贫铬敏化作用，仅采用降低碳含量、稳定化处理、局部固溶热处理等传统方法是不能完全防止的。最近对晶界结构的研究表明，敏化作用强烈地依赖于晶界特征和原子结构，低能晶界如重合位置晶格（CSL）晶界对晶间腐蚀具有强的抵抗力。晶界设计与控制的概念已发展成为晶界工程学（GBE）。GBE材料的特征在于高频率的CSL边界，其抵抗材料的晶间劣化，例如晶间腐蚀。为了提高抗GBE敏化的能力，进行了形变热处理。对304奥氏体不锈钢进行了冷轧 ...更多信息 艾德和固溶热处理，然后敏化热处理。用取向成像显微镜（OIM）观察了晶界特征分布。通过电化学动电位再活化（EPR）和硫酸铁-硫酸试验评价了合金的抗晶间腐蚀性能。晶间腐蚀的敏感性降低的热机械处理，并表示在一个小的轧辊减少最小。CSL边界的频率在小的减少处显示出最大值。硫酸铁-硫酸试验表明，热机械处理试样的腐蚀速率比基材小得多。形变热处理后的试样中观察到高密度的退火孪晶.结果表明，形变热处理可以通过退火孪晶在晶界网络中引入低能段，并可以阻止晶间腐蚀从表面的渗透。研究了GBE过程中碳含量和其它微量元素对晶界特征分布和热力学参数优化的影响。少

Sensitization by chromium depletion due to chromium carbide precipitation at grain boundaries in austenitic stainless steels can not be prevented perfectly only by previous conventional techniques, such as reduction of carbon content, stabilization-treatment, local solution-heat-treatment, etc. Recent studies on grain boundary structure have revealed that the sensitization depends strongly on grain boundary character and atomic structure, and that low energy grain boundaries such as coincidence-site-lattice(CSL) boundaries have strong resistance to intergranular corrosion. The concept of "grain boundary design and control" has been developed as grain boundary engineering (GBE). GBEed materials are characterized by high frequencies of CSL boundaries which are resistant to intergranular deterioration of materials, such as intergranular corrosion. A thermomechanical treatment was hid to improve the resistance to the sensitization by GBE. A type 304 austenitic stainless steel was cold-roll … More ed and solution-heat-treated, and then sensitization-heat-treated. The grain boundary character distribution was examined by orientation imaging microscopy (OIM). The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction. The frequency of CSL boundaries indicated a maximum at the small reduction. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanical-treated specimen than in the base material. A high density of annealing twins were observed in the thermomechanical -treated specimen. The results suggest that the thermomechanical treatment can introduce low energy segments in the grain boundary network by annealing twins and can arrest the percolation of intergranular corrosion from the surface. The effects of carbon content and other minor elements on optimization in grain boundary character distribution (GBCD) and thermomechanical parameters wore also examined during GBE. Less