采用350 keV He+离子束在300 ℃下对沉积态和固溶态选区激光熔化成形(Selective laser melting,SLM)304L不锈钢进行辐照,辐照剂量为5×1016 ions/cm2,随后进行600 ℃保温1 h退火处理.利用透射电子显微镜(TEM)、正电子湮灭和纳米压痕仪研究氦泡的长大与材料硬化行为.系统对比了沉积态和固溶态两种状态的SLM 304L样品,结果表明:600 ℃退火处理时,沉积态SLM 304L不锈钢表现出优异的抗氦泡粗化能力,主要是由于沉积态样品中高密度位错和纳米析出物-基体界面等作为缺陷阱,有效抑制氦泡生长.此外,沉积态样品比固溶态样品具有更高的抗辐照硬化性能,退火处理后两者的硬化率分别为19%和51%.Orowan模型的计算表明,氦泡粗化程度的差异是造成两种状态下SLM 304L不锈钢硬化率不同的主要原因.
The as-built and solution-annealed selective laser melting 304L stainless steel(SLM 304L SS)were implanted with 350 keV He+at 300 ℃ to fluxes of 5×1016 ions/cm2 and then annealed at 600 ℃ for 1 h.The helium bubble growth and irradiation hardening in SLM 304L SS were in-vestigated by TEM,positron annihilation,and nanoindentation measurements.Compared those between two variants of SLM 304L SS,one in as-built condition and the other solution-annealed,the results indicates that the as-built sample of the SLM 304L SS exhibited the outstanding re-sistance to helium bubble growth in the post-irradiation annealed at 600 ℃.Because abundant defect sinks,including high dislocation densities and interfaces between nano-inclusions and the matrix,can effectively inhibit the helium bubble coarsening.Additionally,the hardening rate of the as-built sample is 19%whereas that of the solution-annealed sample is 51%after annealing.According to the calculation of Orowan model,the difference of helium bubble coarsening is the main reason for the different hardening rate of SLM 304L stainless steel in two states.