基于原奥氏体晶界浸蚀机理，通过评价低活化铁素体/马氏体钢原奥氏体晶界的显示效果，对浸蚀剂的配方、缓蚀剂含量及浸蚀时间进行了研究。结果表明：该钢在氯化铁+硝酸水溶液中可以浸蚀出马氏体板条及板条界面处弥散分布着的形貌与尺寸不同的细小析出相，而原奥氏体晶界显示效果不佳；饱和苦味酸水溶液+缓蚀剂能浸蚀出清晰的晶界。缓蚀剂过少，浸蚀速率过高，控制难度较大，达不到抑制晶内组织显像的效果；缓蚀剂过多，易在金属表面吸附成膜，浸蚀速率过低，晶界和晶内组织的浸蚀显像同时受到抑制。在100 mL饱和苦味酸水溶液+0.8 g缓蚀剂中微沸热浸蚀4 min，该钢的晶界清晰可辨。对比能谱分析结果可知，最优浸蚀配方的金相图能更直观地辨识出晶界和晶粒大小，对制样要求较低，图片采集过程更加简单、高效。

Based on the etching mechanism of prior austenite grain boundary, the display effect of prior austenite grain boundary in low activation ferrite/martensitic steel was evaluated, and the formulation of etchant, the content of corrosion inhibitor and the etching time were studied. The results show that the martensitic lath and the fine precipitates with different morphologies and sizes of the steel could be etched out in ferric chloride and nitric acid solution, but the display effect of prior austenite grain boundary was not good. Saturated picric acid solution and corrosion inhibitor can etch clear grain boundaries. If there were too few corrosion inhibitor, the etching rate was too high, and it was difficult to control, which could not achieve the effect of inhibiting the imaging of intragranular structure. If there was too much corrosion inhibitor, it was easy to adsorb and form film on the metal surface, and the etching rate was too low, so the corrosion imaging of grain boundary and intragranular structure was inhibited at the same time. In 100 mL saturated picric acid solution and 0.8 g corrosion inhibitor slightly boiling etching for 4 min, the grain boundaries of the steel were clearly identified. Compared with energy spectrum analysis results, the metallographic diagram of optimal etching formulation could identify the grain boundary and grain size more intuitively, and the requirements for sample preparation were lower, and the image acquisition process was more simple and efficient.