低エネルギー He イオンを照射した純鉄多結晶の低温脆化

tests at 90 K. The plastic behavior of irradiated specimens were compared with that of unirradiated ones. Irradiated specimens showed inter-and transgranular fracture with little plastic deformation by slip, while unirradiated ones deformed by slip to failure. The suppression of slip in irradiated specimens indicates that the surface damage makes the formation and operation of dislocation sources difficult. In addition to the suppression of slip, the decohesion of grain boundaries weakened by He atoms may be responsib豆e for the Iow tempera-