The effect of phosphorous on the hot-ductility of SA508Gr.4N reactor pressure vessel (RPV) steel has been studied. The investigation is done with the use of a Gleeble machine in conjunction with optical metallography, scanning electron microscopy, and transmission electron microscopy. It is observed that both the undoped and P-doped steels exhibit hot-ductility troughs between 750 and 900 °C. However, the trough for the P-doped steel is much shallower than that for the undoped steel. At around 850 °C, the reduction of area (RA) of the undoped steel is quite low (~50%), in comparison to the P-doped steel (~75%). Since there is no grain-boundary precipitation of ferrite and carbides in both undoped and P-doped samples over this temperature range, it can be inferred that the enhancement in hot-ductility for the P-doped steel is independent of these two factors. Grain-boundary microanalysis shows the presence of grain-boundary segregation of P in the tested P-doped samples, implying that the P-induced hot-ductility improvement of this RPV steel may arise from the suppression of grain-boundary sliding by P grain-boundary segregation. Undoubtedly, the present effect of P is unusual and the underlying mechanism for this effect has been briefly discussed. It needs to be underlined that a minor addition of P can play a positive role in the hot-ductility improvement of SA508Gr.4N RPV steel.

研究了磷对SA508Gr.4N反应堆压力容器（RPV）钢热延展性的影响。该研究是通过使用Gleeble机器与光学金相，扫描电子显微镜和透射电子显微镜相结合完成的。可以观察到，未掺杂和掺杂P的钢都在750至900°C之间显示出热延性谷。但是，P掺杂钢的槽比未掺杂钢的槽浅得多。与掺杂P的钢（〜75％）相比，在850°C左右，未掺杂的钢的面积减小率（RA）很小（〜50％）。由于在此温度范围内，未掺杂和P掺杂样品中都没有铁素体和碳化物的晶界沉淀，可以推断，P掺杂钢的热延展性的提高与这两个因素无关。晶界显微分析表明，在测试的掺P样品中存在P的晶界偏析，这表明该RPV钢的P诱导热延性提高可能是由于P晶粒抑制了晶界滑动所致。边界隔离。毫无疑问，P的当前作用是不同寻常的，并且已经简要讨论了该作用的潜在机理。需要强调的是，少量添加P可以对SA508Gr.4N RPV钢的热延展性起积极作用。这表明该RPV钢的P诱导热延性提高可能是由于P晶界偏析对晶界滑动的抑制所致。毫无疑问，P的当前作用是不同寻常的，并且已经简要讨论了该作用的潜在机理。需要强调的是，少量添加P可以对SA508Gr.4N RPV钢的热延展性起积极作用。这表明该RPV钢的P诱导热延性提高可能是由于P晶界偏析对晶界滑动的抑制所致。毫无疑问，P的当前作用是不同寻常的，并且已经简要讨论了该作用的潜在机理。需要强调的是，少量添加P可以对SA508Gr.4N RPV钢的热延展性起积极作用。