Abstract. The relative advantages of the X-ray and classical methods for the determination of phase boundaries in metallurgical equilibrium diagrams are discussed. For ordinary equilibrium diagram work at the higher temperatures, the classical methods appear more satisfactory and reliable, but the X-ray methods become increasingly valuable at the lower temperatures, provided that sufficiently long periods of annealing are used. The X-ray methods are of the greatest value in alloys in which superlattice transformations are involved. The difficulties of determining the composition of the filings comprising the X-ray specimen are emphasized, and also the dangers likely to arise from decomposition of filings during quenching. The general conclusion drawn is that the X-ray and classical methods should be used in conjunction, and that it is a mistake to rely on X-ray methods alone.

Print publication: Issue 5 (May 1941)