The Type 316 steel was received in the form of cold-worked and annealed 0·686 mm-thick strip; the analysis is given in Table I. equilibrium type. This paper describes the experimental observations outlined previously4 and considers the theoretical aspects of the grain-boundary segregation of boron in solution-treated and quenched austenitic steels.Samples of the strip were solution-treated in argon at temperatures in the range 900-1350°C and either quenched to room temperature in a stream of cold argon (cooling rate '" 50 degC/s) or quenched in water at OOC (cooling rate ",500 degC/s). The location and distribution of the boron in the specimens were studied using an optical microscope autoradiographic technique;5 in addition, the samples were examined by optical microscopy and electron microscopy of thin foils and carbon-extraction replicas.The boron autoradiographs of specimens solution-treated at 1350°C for 0·5 h to produce a grain size of 160 J.lm, furnace-cooled to a temperature Ti in the range 900~Ti~1350 o C, held 0·5 h, and argon-quenched to room temperature are shown in Fig. 1. The segregation of boron to the grain-boundary regions is particularly marked after quenching from 1350°C ( Fig. l(a)) and decreases with decreasing temperature such that no intergranular segregation can be detected after quenching from 900°C ( Fig. 1(1)). A qualitatively similar increase in the grain-boundary segregation of boron with increasing solution-treatment temperature was also observed in samples of the steel strip argon-quenched after annealing at 1000, 1100, and 1200°C and with grain sizes of 50, 85, and 125 J.lm,respectively.The autoradiographs of specimens solution-treated at 1200°C for 0·5 h, furnace-cooled to a temperature Ti in the range 1000~Ti < 1200°C, held 0·5 h, and either argonquenched to room temperature or water-quenched to DoC are shown in Fig. 2. These results clearly demonstrate that segregation of the boron to the grain-boundary regions only occurs after the slower quench from the higher solution':' treatment temperatures, there being no evidence of intergranular boron segregation in any of the samples waterquenched from temperatures in the range 1000-1200 o C.

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