奥氏体不锈钢焊接接头辐照偏析和辐照硬化的研究

Study on Radiation Segregation and Irradiation Hardening of Austenitic Stainless Steel Weld Joints

为探究奥氏体不锈钢焊接接头辐照后的晶界偏析和硬化规律,实验采用剂量为2×10^17 n/cm^2、100 keV的He+对三组不同焊接参数的316L焊接接头进行辐照,并对其辐照前后的硬度、微观结构和晶界成分进行了表征。辐照后焊接接头的TEM结果表明出现了位错环、位错缠结、位错墙、位错胞和氦泡等辐照诱导的特征微结构,但其尺寸和密度与焊接参数并无明显的关联;晶界的EDS数据表明,辐照诱导的偏析会导致焊缝原本富Cr贫Ni的晶界出现富Ni贫Cr的现象;辐照前后的显微硬度数据表明,辐照后硬度的增量随着热输入增大而减小。因此,奥氏体不锈钢焊接接头辐照偏析和辐照后显微结构的变化与普通奥氏体不锈钢类似;晶粒尺寸随着焊接热输入减小而减小,而晶粒细化使晶粒内位错通道密度增大,辐照产生的高密度缺陷对位错滑移的阻碍作用就越明显,则辐照硬化增量会随着热输入的增大而减小。

To investigate the grain boundary segregation and hardening of austenitic stainless steel weld joints after helium ion irradiation,three groups of 316L weld joints under different welding parameters were irradiated by He+at doses of 2×10^17 n/cm^2 and 100 keV.The hardness,microstructure and grain boundary composition of the welding joints were characterized before and after helium ion irradiation.TEM observation revealed that the characteristic irradiated microstructure of weld joints were dislocation loop,dislocation tangle,dislocation wall,dislocation cell and helium bubble,in the size and density,which were not significantly related to the welding parameters.EDS data of grain boundary indicated that the segregation induced by irradiation showed the appearance of Ni-rich and Cr-poor in the original to Cr-rich and Ni-poor in grain bcoundary of weld joints.The microhardness data before and after helium ion irradiation showed that the increase of hardness decreased with the increment of heat input.Therefore,the grain boundary segregation and microstructure change of the weld joints of austenitic stainless steel after irradiation were similar to that of the base metal.The grain size decreased with the decrement of welding heat input,which improved the dislocation channel density in the grains.As a result,the effect of high density defects produced by irradiation were more obvious on the slip resistance.The irradiation hardening increment decreased with increasing heat input in consequence.