不锈钢和铝合金在典型环境中的应力腐蚀特征与检测方法
发布时间：2018-07-15 12:20
【摘要】：奥氏体不锈钢和铝合金由于具有良好的加工性能和耐腐蚀性能,在核电站、航空、海洋运输等领域具有广泛的应用,但是应力腐蚀开裂(SCC)成为这些材料在应用过程中最大的危险之一。因此,本文基于304奥氏体不锈钢(304SS)、01570铝合金、7A60铝合金和2195铝合金在典型环境中的应力腐蚀损伤特征和腐蚀机理展开研究。首先,基于电化学噪声(EN)方法,提出采用小波分形维数D鉴别304SS的腐蚀类型。结果表明,小波分形维数D可以表征腐蚀在304SS电极表面的局部程度,腐蚀越全面均匀地分布在电极表面,小波分形维数越大,反之则值越小。并采用小波分形维数分析了Q235碳钢钢筋在模拟混凝土孔隙溶液中的腐蚀过程,试样表面为钝化态时D值保持在2以上,发生点蚀后D值开始下降到1.75左右,然后持续下降到1.1~1.2,说明局部腐蚀更加深入基体,与304SS的试验结果一致。采用EN和声发射(AE)原位检测技术,结合扫描电子显微镜(SEM)研究了敏化处理304SS在0.5mol/L Na2S2O3溶液中的沿晶应力腐蚀(IGSCC)行为,以及固溶处理304SS在4mol/L NaCl+0.01mol/L Na2S2O3溶液(TGSCC1)和0.5mol/L NaCl+1.5mol/L H2SO4溶液(TGSCC2)中的穿晶应力腐蚀(TGSCC)行为。结果表明EN暂态峰、AE信号以及应力变化速率峰之间具有对应关系,而噪声电阻Rn、电流标准偏差SI、累积波击数和累积能量可以表征应力腐蚀的不同阶段。采用K-means聚类法对AE数据进行分析,采用小波分形维数D分析EN,AE聚类结果与EN小波分形维数结果在表征腐蚀类型上具有一致性。另外,采用透射电子显微镜(TEM)、SEM和和能量散射X射线谱(EDS)等技术研究了不可热处理强化01570铝合金、析出强化7A60铝合金以及2195铝合金在3.5%NaCl溶液中的应力腐蚀行为。结果表明对于不可热处理强化的01570铝合金,其应力腐蚀敏感性主要受晶内位错数量以及分布的影响,随着退火温度的升高,残余应力得以有效释放,抗应力腐蚀性能提高;对于7A60铝合金,应力腐蚀敏感性随晶界析出相η(MgZn2)的粗化和相间距变大而降低;然而晶界析出相T1(Al2CuLi)对2195铝合金的应力腐蚀敏感性没有明显影响。
[Abstract]:Austenitic stainless steel and aluminum alloy are widely used in nuclear power plant, aviation, marine transportation and other fields because of their good processability and corrosion resistance. However, stress corrosion cracking (SCC) becomes one of the greatest dangers in the application of these materials. Therefore, this paper is based on 304 austenitic stainless steel (304SS), 01570 aluminum alloy, 7A60 The stress corrosion damage characteristics and corrosion mechanism of aluminum alloy and 2195 aluminum alloy in typical environment are studied. First, based on the electrochemical noise (EN) method, the wavelet fractal dimension D is proposed to identify the corrosion types of 304SS. The results show that the wavelet fractal dimension D can characterize the local degree of corrosion on the surface of 304SS electrode, and the more comprehensive the corrosion is. The larger the fractal dimension of the wavelet is, the smaller the fractal dimension is, and the smaller the value is, and the fractal dimension of the wavelet is used to analyze the corrosion process of the Q235 steel bar in the simulated concrete pore solution. When the surface of the sample is passivated, the D value is above 2, and the D value begins to fall to about 1.75 after the pitting and then continues to fall to the 1.1~1.2. The local corrosion is more deep in the matrix, which is in agreement with the experimental results of 304SS. The behavior of the intergranular stress corrosion (IGSCC) in the sensitized treatment of 304SS in 0.5mol/L Na2S2O3 solution, and the solution treatment 304SS in 4mol/L NaCl+0.01mol/L Na2S2O3 solution, are studied by EN harmonic emission (AE) in situ detection technology and scanning electron microscope (SEM). The transgranular stress corrosion (TGSCC) behavior in the 0.5mol/L NaCl+1.5mol/L H2SO4 solution (TGSCC2) shows that there is a corresponding relationship between the transient peak of EN, the AE signal and the rate peak of the stress change, while the noise resistance Rn, the current standard deviation SI, the cumulative wave number and the cumulative energy can be used to characterize the different stages of the stress corrosion. The K-means clustering method is used. The AE data is analyzed and the wavelet fractal dimension D is used to analyze EN. The result of AE clustering and the fractal dimension result of EN wavelet are consistent with the corrosion type. In addition, the 01570 aluminum alloy is strengthened by transmission electron microscope (TEM), SEM and energy scattering X ray spectrum (EDS). The precipitation intensification of 7A60 aluminum alloy is obtained. The stress corrosion behavior of 2195 aluminum alloy in 3.5%NaCl solution shows that the stress corrosion sensitivity is mainly influenced by the number and distribution of the intragranular dislocation for the 01570 aluminum alloy reinforced by the non heat treatment. With the increase of annealing temperature, the residual stress is effectively released and the resistance to stress corrosion is improved; for the 7A60 aluminum alloy, the stress corrosion resistance should be improved. The sensitivity of force corrosion decreases with the coarsening of the precipitation phase (MgZn2) and the interphase spacing in the grain boundary, but the precipitated phase T1 (Al2CuLi) has no significant effect on the stress corrosion sensitivity of 2195 aluminum alloy.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG172.9
，
本文编号：2124054
[Abstract]:Austenitic stainless steel and aluminum alloy are widely used in nuclear power plant, aviation, marine transportation and other fields because of their good processability and corrosion resistance. However, stress corrosion cracking (SCC) becomes one of the greatest dangers in the application of these materials. Therefore, this paper is based on 304 austenitic stainless steel (304SS), 01570 aluminum alloy, 7A60 The stress corrosion damage characteristics and corrosion mechanism of aluminum alloy and 2195 aluminum alloy in typical environment are studied. First, based on the electrochemical noise (EN) method, the wavelet fractal dimension D is proposed to identify the corrosion types of 304SS. The results show that the wavelet fractal dimension D can characterize the local degree of corrosion on the surface of 304SS electrode, and the more comprehensive the corrosion is. The larger the fractal dimension of the wavelet is, the smaller the fractal dimension is, and the smaller the value is, and the fractal dimension of the wavelet is used to analyze the corrosion process of the Q235 steel bar in the simulated concrete pore solution. When the surface of the sample is passivated, the D value is above 2, and the D value begins to fall to about 1.75 after the pitting and then continues to fall to the 1.1~1.2. The local corrosion is more deep in the matrix, which is in agreement with the experimental results of 304SS. The behavior of the intergranular stress corrosion (IGSCC) in the sensitized treatment of 304SS in 0.5mol/L Na2S2O3 solution, and the solution treatment 304SS in 4mol/L NaCl+0.01mol/L Na2S2O3 solution, are studied by EN harmonic emission (AE) in situ detection technology and scanning electron microscope (SEM). The transgranular stress corrosion (TGSCC) behavior in the 0.5mol/L NaCl+1.5mol/L H2SO4 solution (TGSCC2) shows that there is a corresponding relationship between the transient peak of EN, the AE signal and the rate peak of the stress change, while the noise resistance Rn, the current standard deviation SI, the cumulative wave number and the cumulative energy can be used to characterize the different stages of the stress corrosion. The K-means clustering method is used. The AE data is analyzed and the wavelet fractal dimension D is used to analyze EN. The result of AE clustering and the fractal dimension result of EN wavelet are consistent with the corrosion type. In addition, the 01570 aluminum alloy is strengthened by transmission electron microscope (TEM), SEM and energy scattering X ray spectrum (EDS). The precipitation intensification of 7A60 aluminum alloy is obtained. The stress corrosion behavior of 2195 aluminum alloy in 3.5%NaCl solution shows that the stress corrosion sensitivity is mainly influenced by the number and distribution of the intragranular dislocation for the 01570 aluminum alloy reinforced by the non heat treatment. With the increase of annealing temperature, the residual stress is effectively released and the resistance to stress corrosion is improved; for the 7A60 aluminum alloy, the stress corrosion resistance should be improved. The sensitivity of force corrosion decreases with the coarsening of the precipitation phase (MgZn2) and the interphase spacing in the grain boundary, but the precipitated phase T1 (Al2CuLi) has no significant effect on the stress corrosion sensitivity of 2195 aluminum alloy.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG172.9
，
本文编号：2124054
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