将经过不同加工工艺处理的N18锆合金样品放入高压釜中, 在360 ℃/18.6 MPa/0.01 mol/L LiOH水溶液中进行310 d的长期腐蚀, 用TEM和SEM观察样品的显微组织, 研究加工工艺对N18合金腐蚀行为的影响. 结果表明, 样品在冷轧退火处理之前进行$\beta$相水淬处理, 得到尺寸在几十纳米均匀弥散分布的第二相, 其耐腐蚀性能最好; 提高加工过程中的中间退火温度至740 ℃, 样品由于第二相长大到数百纳米使耐腐蚀性能明显变坏, 腐蚀到150 d时发生转折, 转折后的腐蚀速率急剧增加; 样品经780 ℃保温2 h和800 ℃保温2 h处理后, 其显微组织中存在β-Zr, 这对N18锆合金的耐腐蚀性能是有害的, 但只要在后续的加工热处理过程中能使β-Zr分解, 获得细小的第二相, 则合金的耐腐蚀性能可恢复到较好的水平.
The effect of thermal processing on corrosion behavior of N18 alloy has been investigated by autoclave tests in 0.01 mol/L LiOH aqueous solution at 360 ℃ and l8.6 MPa, and the microstructures of these specimens were examined by TEM and SEM. The results show that the corrosion resistance of specimens is improved obviously by $\beta$ phase quenching before cold rolling and annealing due to nano second phase particles (SPPs) precipitated dispersively, but when the intermediate annealing temperature increased to 740 ℃ before cold rolling and annealing, the corrosion resistance is lowered greatly due to SPPs coarsened to several hundred nanometers, where the corrosion rate accelerates markedly after the corrosion transition at 150 d exposure. The existence of β-Zr phase in the microstructures of specimens treated at 780 and 800 ℃ for 2 h in dual phase region is harmful to the corrosion resistance, but the corrosion resistance returns to a better level after the decomposition of β-Zr phase during the following processes of cold rolling and annealing at 580 ℃ to obtain fine SPPs.
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