Structural and analytical electron microscopy of dislocation loops and precipitates formed during ageing of an α‐bombarded MnCr austenitic steel

Solution annealed samples of the MnCr austenitic steel Nitronic 32 are uniformly implanted at 310 K with 500 atppm He corresponding to a dose of ≈ 0.1 dpa. Specimens are subsequently aged, one set at 773 K and another set at 1023 K; the evolution of the dislocation structure and the related segregation and precipitation phenomena are examined by TEM, EELS, and electron diffraction. Short annealing (2 h) at 1023 K lead to the formation of Frank interstitial dislocation loops which are found enriched in N and Cr. After longer annealing (25 h) at 1023 K, Cr₂N precipitated on the loops, small He bubbles becomes visible in the matrix, whereas no lamellar precipitation is observed in contrast to unirradiated specimens.