【摘要】：奧氏體不銹鋼和鋁合金由于具有良好的加工性能和耐腐蝕性能,在核電站、航空、海洋運(yùn)輸?shù)阮I(lǐng)域具有廣泛的應(yīng)用,但是應(yīng)力腐蝕開裂(SCC)成為這些材料在應(yīng)用過程中最大的危險(xiǎn)之一。因此,本文基于304奧氏體不銹鋼(304SS)、01570鋁合金、7A60鋁合金和2195鋁合金在典型環(huán)境中的應(yīng)力腐蝕損傷特征和腐蝕機(jī)理展開研究。首先,基于電化學(xué)噪聲(EN)方法,提出采用小波分形維數(shù)D鑒別304SS的腐蝕類型。結(jié)果表明,小波分形維數(shù)D可以表征腐蝕在304SS電極表面的局部程度,腐蝕越全面均勻地分布在電極表面,小波分形維數(shù)越大,反之則值越小。并采用小波分形維數(shù)分析了Q235碳鋼鋼筋在模擬混凝土孔隙溶液中的腐蝕過程,試樣表面為鈍化態(tài)時(shí)D值保持在2以上,發(fā)生點(diǎn)蝕后D值開始下降到1.75左右,然后持續(xù)下降到1.1~1.2,說明局部腐蝕更加深入基體,與304SS的試驗(yàn)結(jié)果一致。采用EN和聲發(fā)射(AE)原位檢測技術(shù),結(jié)合掃描電子顯微鏡(SEM)研究了敏化處理304SS在0.5mol/L Na2S2O3溶液中的沿晶應(yīng)力腐蝕(IGSCC)行為,以及固溶處理304SS在4mol/L NaCl+0.01mol/L Na2S2O3溶液(TGSCC1)和0.5mol/L NaCl+1.5mol/L H2SO4溶液(TGSCC2)中的穿晶應(yīng)力腐蝕(TGSCC)行為。結(jié)果表明EN暫態(tài)峰、AE信號(hào)以及應(yīng)力變化速率峰之間具有對應(yīng)關(guān)系,而噪聲電阻Rn、電流標(biāo)準(zhǔn)偏差SI、累積波擊數(shù)和累積能量可以表征應(yīng)力腐蝕的不同階段。采用K-means聚類法對AE數(shù)據(jù)進(jìn)行分析,采用小波分形維數(shù)D分析EN,AE聚類結(jié)果與EN小波分形維數(shù)結(jié)果在表征腐蝕類型上具有一致性。另外,采用透射電子顯微鏡(TEM)、SEM和和能量散射X射線譜(EDS)等技術(shù)研究了不可熱處理強(qiáng)化01570鋁合金、析出強(qiáng)化7A60鋁合金以及2195鋁合金在3.5%NaCl溶液中的應(yīng)力腐蝕行為。結(jié)果表明對于不可熱處理強(qiáng)化的01570鋁合金,其應(yīng)力腐蝕敏感性主要受晶內(nèi)位錯(cuò)數(shù)量以及分布的影響,隨著退火溫度的升高,殘余應(yīng)力得以有效釋放,抗應(yīng)力腐蝕性能提高;對于7A60鋁合金,應(yīng)力腐蝕敏感性隨晶界析出相η(MgZn2)的粗化和相間距變大而降低;然而晶界析出相T1(Al2CuLi)對2195鋁合金的應(yīng)力腐蝕敏感性沒有明顯影響。
[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.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TG172.9
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本文編號(hào)：2124054