C含量及冷变形对OCr25Ni35AlTi合金组织和性能的影响

发布时间：2019-01-01 11:00

【摘要】：0Cr25Ni35AlTi是我国自主研发的一种适用于苛刻环境的Fe-Ni-Cr合金,具有优良耐晶间腐蚀和力学性能,可应用在压水堆装置蒸汽发生器传热管。0Cr25Ni35AlTi合金力学性能和耐蚀性的匹配与合金成分密切相关,尤其合金中的C含量对合金的性能有极大的影响。因此,通过系统地研究C含量对合金的性能的影响规律,对于优化0Cr25Ni35AlTi合金成分和加工工艺具有重要的实用价值。本文采用光学显微镜、扫描电镜、透射电镜和物理化学相等方法对不同C含量的0Cr25Ni35AlTi合金的组织、力学性能、析出相以及变形特性进行了测试,,并应用失重法和电化学方法研究了合金耐蚀性能。研究结果表明：0Cr25Ni35AlTi合金随着碳含量的增加,其平均晶粒尺寸减小,M23C6析出量增加,合金的力学性能提高,但合金的耐晶间腐蚀性能下降,当合金中C含量控制在0.025%左右,具有良好的耐晶间腐蚀性能,且其强度仍能保持在300MPa以上,满足合金的应用性能指标。冷变形会对0Cr25Ni35AlTi合金的力学性能和耐蚀性能产生明显的影响,随着变形量增加,组织中变形带增多变密,孪晶数量增加而且发生弯曲变形,导致合金的强度、硬度增加,塑性降低,加工硬化能力降低,同时合金的耐点蚀性能降低。随着碳含量增加,合金中析出数量增加且聚集长大,耐蚀性降低。其中合金在650℃时效处理2h后,由于晶界区域铬出现严重贫化,耐晶间腐蚀性能最差。基于热压缩实验建立了0Cr25Ni35AlTi合金的热变形本构方程,该方程可以描述合金在热变形过程中变形温度、应变速率和峰值应力的关系。通过观察不同热变形条件下的再结晶行为,发现增加变形温度或者减小应变速率,有利于合金热变形过程中发生动态再结晶。碳含量对0Cr25Ni35AlTi合金动态再结晶过程产生明显的影响,随着碳含量增加,合金的动态再结晶进程越迟缓。同时变形激活能增加,变形难度增大。
[Abstract]:0Cr25Ni35AlTi is a self-developed Fe-Ni-Cr alloy suitable for harsh environment. It has excellent intergranular corrosion resistance and mechanical properties. The matching of mechanical properties and corrosion resistance of 0Cr25Ni35AlTi alloy is closely related to the composition of the alloy, especially the content of C in the alloy has a great influence on the properties of the alloy. Therefore, it is of great practical value to optimize the composition and processing technology of 0Cr25Ni35AlTi alloy by systematically studying the effect of C content on the properties of the alloy. In this paper, the microstructure, mechanical properties, precipitation phase and deformation characteristics of 0Cr25Ni35AlTi alloy with different C content were measured by optical microscope, scanning electron microscope, transmission electron microscope and physicochemical equivalent method. The corrosion resistance of the alloy was studied by weight loss method and electrochemical method. The results show that with the increase of carbon content, the average grain size of 0Cr25Ni35AlTi alloy decreases, the amount of M23C6 precipitates increases, the mechanical properties of the alloy increase, but the intergranular corrosion resistance of the alloy decreases, when the content of C in the alloy is controlled at about 0.025%. It has good intergranular corrosion resistance, and its strength can still be kept above 300MPa, which meets the application performance index of the alloy. Cold deformation has an obvious effect on the mechanical properties and corrosion resistance of 0Cr25Ni35AlTi alloys. With the increase of deformation amount, the deformation bands in the microstructure become more dense, the number of twins increases and the bending deformation occurs, which results in the increase of the strength and hardness of the alloy. The plasticity is reduced, the work hardening ability is decreased, and the pitting corrosion resistance of the alloy is decreased. With the increase of carbon content, the amount of precipitation in the alloy increases, and the corrosion resistance decreases. After aging at 650 鈩，

本文编号：2397463