Interaction of helium with irradiation defects in metals

在这种情况下，氦在晶界的积累量很大，导致晶间脆化。这种情况在氚特技技术和回旋加速器注入技术中最为明显。在深冷放电条件下，在产生氦的同时引入位移损伤，产生的氦立即被空位俘获，氦的脆性显著降低。由于这种情况与聚变环境非常相似，这一发现导致了一个非常重要的结论，即氦的脆化可能没有预期的那么显著。溶质原子和氦之间的相互作用与溶质原子尺寸因子之间的明显关联变得明显。也就是说，严重偏小的溶质，如铁和铬，强烈地捕获氦并抑制其扩散。这一发现是通过对注入氦的样品在置换热冲击能量下进行的透射电子显微镜和THDS实验获得的。这种小尺寸溶质的这种性质可能会有效地抑制高温下的氦脆。

A coherent picture on the interaction of helium with irradiation defects has been established as a result of the present project : When displacement damage is significantly less than the amount of helium introduced, the fraction of interstitial helium is large and they diffuse very rapidly. Accumulation of helium to grain boundaries is high in this case leading to intergranular embrittlement. This situation is most pronounced for tritium trick technique and cyclotron implantation follows. When speciments doped with helium using tritium trick technique are irradiated with neutrons, helium is trapped mainly by irradiation-induced vacancies and helium transport to grain boundaries is suppressed and embrittlement is mitigated. Under DHCE condition where displacement damage is introduced concurrently with helium generation, helium generated is immediately trapped by vacancies and helium embrittlement has been found significantly reduced. Since this situation is quite similar to fusion environment, this finding leads to a very important conclusion that helium embrittlement may not be so significant as has been anticipated.A clear correlation of the interaction between solute atoms and helium with solute atomic size factor became evident. Namely, strongly undersized solutes, e.g.iron and chromium, traps helium strongly and suppress their diffusion. This finding was obtained from TEM and THDS experiments on speciments helium-injected with an energy under displacement thershold energy. This kind of property of undersized solutes may be effective in suppressing helium embrittlement at high temperatures.