微硬度压痕对小冲杆测试的影响研究

Effect of Introduced Indents by Micro-indentation Tests on Small Punch Tests

由于有限的辐照面积,小试样测试技术对核材料的辐照损伤研究具有重要的意义。微硬度和小冲杆测试可以有效评估材料的辐照硬化和脆化,然而微硬度压痕的引入对小冲杆实验结果的影响需要进行探讨。针对国产反应堆压力容器钢A508-3和其模型合金(Fe-1.35Mn-0.75Ni),研究了随机引入的压痕对后续小冲杆测试结果的影响。首先,微硬度和小冲杆的结果表明,A508-3的硬度明显高于其模型合金,并且伴随明显的延性提升。电子背散射衍射结果(EBSD)表明,A508-3和其模型合金的晶粒分布基本均匀,且A508-3的晶粒明显小于其模型合金。A508-3的硬度高于模型合金主要是由于细晶强化和固溶强化,而延展性提升主要是由于增加的晶粒和晶界密度。其次,小冲杆结果表明,由小冲杆测试得到的最大应力P_(max)在较软的模型合金中会受到压痕的明显影响。而延展性方面,小冲杆测试结果基本不受引入压痕的影响。结合实际的测试环境,对于实际应用的核材料,压痕的引入不会对小冲杆评估材料的延性损失产生影响。

Due to the limited irradiation zone,development of small-scale test technology is of significant importance for the investigation of irradiation damage in nuclear materials.Micro-indentation tests and small punch tests(SPT)can efficiently evaluate irradiation hardening and embrittlement.However,the influence of the introduced indents by the micro-indentation tests to the SPT investigation need to be clarified and investigated.In the present study,the A508-3,a Chinese reactor pressure vessel(RPV)steel,and its model alloy(Fe-1.35Mn-0.75Ni)were used to investigate the effect of arbitrarily introduced indents on the SPT.Firstly,both micro-indentation tests and SPT indicate that hardness of A508-3 is significantly greater than the model alloy,accompanied by improved ductility.Electron backscattered diffraction(EBSD)results indicate that a quasiuniform distribution of grains was observed in both specimens and the grains in A508-3 were obviously smaller than the model alloy.The strengthening of A508-3 was mainly ascribed to the refined grain strengthening and the solution strengthening.The improved ductility was possibly due to the increasing grain numbers or the density of grain boundaries.Secondly,SPT results indicate that,the obtained maximum load,P_(max)was obviously influenced by the introduced indents in softer specimen(the model alloy).The obtained ductility was hardly influenced by the introduced indents.For the practical materials,the introduced indents are expected to have minor influence on the data obtained by SPT.