Dendrite Arm Spacing in Iron-Carbon-Chromium Alloys

Abstract

Dendrite arm spacings in unidirectionally solidified iron-carbon-chromium alloys with chromium and carbon less than 15% and 2%, respectively, were measured and discussed on the basis of the results for ironbase binary alloy described in the previous paper. The results obtained are as follows:
1) Primary and secondary arm spacings in the iron-carbon-chromium alloys are inversely proportional to the square root and the cube one, respectively, of cooling rate in similar way as those in iron-base binary alloys.
2) Primary arm spacings in the alloys which form γ-iron as the primary phase decrease with increasing the chromium content or with decreasing the carbon content, With the carbon content of the alloys less than the critical value below which the primary phase becomes δ-iron, the arm spacing becomes much larger than not would be expected from the extrapolation of data above the critical value.
3) Secondary arm spacings decrease with increasing the carbon content or chromium content. They arc discontinuously varied by the change from δ-iron to γ-iron in the primary phase.
4) It is shown that a parameter proposed in iron-base binary alloys as expressing the effect of alloying elements on dendrite arm spacings is determined from the ternary phase diagram and is also applicable to the ternary alloy.