ELECTRON DIFFRACTION ANALYSIS OF PRECIPITATES IN A 13NI MARAGING STEEL (280 KGF/MM2).

THE PRECIPITATES HAVE BEEN IDENTIFIED IN RELATION TO THE ORIENTATION OF ″SIGMA″ AND ″DELTA″ PHASES IN THE MARTENSITE MATRIX BY MEANS OF X-RAY AND SELECTED AREA ELECTRON DIFFRACTION ANALYSES. IT WAS SHOWN THAT THE PRECIPITATES AS AN INTERMETALLIC COMPOUND OF ″DELTA″ -(FE, NI, CO)MO ARE RESPONSIBLE FOR STRENGTHENING THE STEEL. AFTER AGING, THE ″MU″ -PHASE APPEARING IN THE AS-FORGED STEEL MAY REDUCE ITS TOUGHNESS. AFTER OVER-AGING, E. G. 580 D. C FOR 16 H AND AIR-COOLED, SOME REVERTED AUSTENITE WAS FORMED. WHEN AGED SPECIMENS HEATED TO 743 D. C IN ELECTRON MICROSCOPES WERE OBSERVED IN SITU, ″DELTA″ GRAINS WERE SEEN TO COALESCE AND THE NEEDLE-LIKE ″SIGMA″PHASE WAS SEEN TO PRECIPITATE. IN CHINESE WITH ENGLISH ABSTRACT.