Journal of Research of the National Bureau of Standards
In order to study the relationship between the metallurgical reactions that occur during aging treatments of 17- 7 PH and the accompanying changes in mechanical properties samples of 0.0025 in. thick foil, annealed at 1950 �F for 1/2 hour and then conditioned at, 1400 �F for 1 _ hours, were given aging treatments at 850 to 1150�F. Bulge test specimens, punched from the aged samples, were tested and used for metallographic, X-ray diffraction and electron diffraction examinations. Electron diffraction patterns obtained from selected areas in carbon extraction replicas showed the presence of ordered ferrite (B2CsC1 type BCC structure) in specimens aged 68 hours at 1050�F. The aging treatments, bulge test data, and austenite contents obtained at 1050�F indicated that the abrupt increase in strength and loss in ductility were caused by immediate formation of the ordered ferrite constituent but the subsequent rapid recovery of ductility and slower loss in strength were caused by a reversion of random ferrite to austenite. At temperatures of 970�F and below, there was no reversion and after the abrupt increase in strength and loss in ductility there was no further change in properties.
Vol. 66C, No. 2, p. 113
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