Papers - Cleveland Meeting – September, 1929 – The Gamma-alpha Transformation in Pure Iron (With Discussion)

The senior author of this paper has expressed the belief that when gamma iron transforms into alpha iron on reaching the A3 point, each gamma grain does not change bodily into one or more alpha grains but that the alpha phase forms first at the boundaries and along the crystallo-graphic planes of the austenite grains.1 To quote: On cooling through the point As, at about 900° C, iron passes from the gamma condition to a new allotropic form generally designated as alpha. This transformation, however, is not instantaneous. There are good reasons for believing that it begins at the grain boundaries and along the octahedral planes of the crystals and that it progresses until each grain of gamma iron is changed into a grain of alpha iron, the resulting structure being similar to that of gamma iron. Were it possible to retain