SEDL / STP / STP955-EB / STP33839S

Ion Damage in a Fe-10Cr-6Mo-0.5Nb Ferritic Steel

Farrell, K
Senior research staff and research staff members, Oak Ridge National Laboratory, Oak Ridge, TN

Lee, EH
Senior research staff and research staff members, Oak Ridge National Laboratory, Oak Ridge, TN

Pages: 10    Published: Jan 1987

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Abstract

An annealed-and-aged ferritic steel containing fine NbC precipitates and relatively coarse particles of Laves phase was bombarded with 4-MeV iron ions to 100 displacements per atom (dpa) at 400 to 600°C. Much of the damage structure consisted of dislocation tangles that coarsened with increasing temperature. Cavity formation began at 450°C, peaked at about 535°C, and was absent at 600°C. Maximum swelling was only 0.2%. The Laves particles exhibited recoil dissolution and restructuring. Bombardments with Fe + He + D or Fe + He beams at ratios of 10 atomic parts per million (appm) He/dpa and 45 appm D/dpa introduced high concentrations of very small bubbles and comparatively few larger, bias-driven cavities. The latter were initiated at bubble clusters on NbC particles. Maximum swelling of 0.75% occurred at 550°C. Recoil dissolution of the Laves phase was retarded by the gases. Large critical cavity sizes and unbalanced dislocation and cavity sink strengths contribute to low swelling of this alloy.