Iron Crystals

Abstract

IT has been found possible to grow long crystals in iron wire by making use of the allotropic transformation which occurs at about 900°C. The method is to heat a portion of the wire between two mercury contacts by passing direct or alternating current through it and then to cause the heated portion to travel along the wire either by moving the support carrying the contacts or by moving the wire itself. The hottest part of the wire should be at 1400°C. or higher. Under these conditions a very steep temperature gradient exists at the point where face centred cubic (γ) crystals, stable at high temperatures, are being replaced by body-centred cubic (α) crystals, stable at lower temperatures, and at a favourable velocity of travel a single -crystal will grow to a length of 20 cm. or more in wire 1 mm. in diameter.