Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： Ferritic stainless steel (FSS) containg (11%~13%)Cr with low C and N has excellent comprehensive performances and thus can be widely applied in extensive fields such as automobile exhaust systems, containers, buses and so on. Among them, 409L steel containing 11%Cr has been increasingly used in applications for tail pipes in the cold end parts of automobile exhaust systems because of its good corrosion resistance and moderate price. During the manufacture process for these tail pipes, improper heat treatments and welding operations cause the precipitation of some detrimental phases such as carbides, nitrides, which leads to a reduction on the resistance to intergranular corrosion (IGC) due to the presence of Cr-depleted zone in the grain boundaries. In this work, the precipitates in grain boundaries of 409L steel aged at 600 ℃ were investigated using TEM, EDS and SAED. The double loop-electrochemical potentiokinetic reactivation (DL-EPR) method was extended for evaluating the IGC susceptibility of 409L steel. The operating conditions of the DL-EPR test for 409L steel were optimized by investigating the influences of the main test parameters, such as scanning rate, solution composition, solution temperature. The experimental results showed that the IGC occurred in aged 409L steel due to the precipitation of M23C6 along grain boundaries. The optimized DL-EPR test could evaluate the IGC susceptibility of 409L steel quantitatively with high reproducibility. With the increase of aging time, much more M23C6 precipitated along grain boundaries, which resulted in 409L steel more susceptible to IGC.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The formation of amorphous phase has been investigated in U-Co system over a wide range of compositions, namely, UxCo100-x (x=50~87.5) by mean of melt-spinning. Phase identification for the arc-melted ingots and rapidly quenched alloys, and the thermal stability of the amorphous phases thus formed have been examined by XRD and DSC, respectively. The component phases in the ingot alloys were structurally the same as those presented in U-Co phase diagram, but were associated with a certain compositional metastability. Rapid quenching experiment revealed that the ease of formation of amorphous phase occurred within the composition range of 58.5≤x≤78, and amorphous phase was most readily formed in the vicinity of U66.7Co33.3 composition. The dynamical crystallization temperatures of the amorphous phases were determined to be 534~550 K at a DSC heating rate of 20 K/min, and the highest reduced crystallization temperature (relative to the liquidus temperature) as calculated to be 0.535, and moreover, the exothermal enthalpies of crystallization were determined to be in a range of 4.8~8.5 kJ/mol. Upon room temperature electrochemical polarization in a 50×10- 6 Cl- electrolyte, these amorphous alloys exhibited corrosion potentials as high as about -50 mV, being much more positive than that of depleted uranium. In these amorphous alloys, it has also been found that the rust resistance performance appears to be parallel to the ease of amorphous phase formation.
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-15 Cooperative journals: 《金属学报》
Abstract：利用TEM，EDS和SAED等分析方法，研究了11Cr 铁素体不锈钢409L在600 ℃敏化下析出物特性，并将双环电化学动电位再活化法(DL-EPR)用于评价409L钢的晶间腐蚀敏感性，通过研究DL-EPR的扫描速率、介质成分、介质温度对测试结果的影响，对该法进行了优化，并用该优化法研究了敏化处理对409L钢晶间腐蚀敏感性的影响。结果表明，敏化的409L钢发生晶间腐蚀是由于M23C6沿晶界析出。在最优化条件下，DL-EPR法能定量评价409L钢的晶间腐蚀敏感性且具有良好的重复性。随敏化处理时间延长，沿晶界析出的M23C6增多，晶间腐蚀敏感性也随之增强。
Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-10 Cooperative journals: 《金属学报》
Abstract：将U-Co二元系中的富U合金UxCo100-x（x = 50~87.5，原子分数，下同）作为研究对象，采用电弧熔炼与甩带方法制备它们的母合金锭与薄带样品，通过X 射线衍射和差示扫描量热分析研究合金样品的相组成与稳定性，同时采用动电位极化方法研究非晶合金的耐腐蚀性能。结果表明，条带非晶形成的成分区间为58.5? x ?78，其最佳成分出现在U66.7Co33.3附近；在20 K/min加热速率下，U-Co非晶的晶化温度位于534~550 K之间，晶化放热焓为4.8~7.9 kJ/mol，约化晶化温度Trx值最高达0.535；在50 x 10-6 Cl-溶液中，U-Co非晶合金的腐蚀电位大都接近-50 mV，其抗腐蚀能力显著优于贫铀，且U-Co非晶耐腐蚀性与其形成能力显示出正相关性。
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