On problems of volume change measurements in lamellar cast iron

Solidification of lamellar cast iron is a complex mechanism due to the contracting austenite phase and the expanding graphite phase precipitation. The combined effect of contraction-expansion has an influence on the volume change related defects (shrinkage porosity and penetration). Critical moments in measuring volume change are the methods used for measurement together with the interpretation of the solidification based on the macrostructure. Reliable results are obtained using displacement measurement in both axial and radial direction of a cylindrical sample in combination with using two thermocouples and a force measurement unit. Common drawback of the used method together with other methods presented in the literature is the early expansion observed before the coherence of the solidifying grains. The introduced force measurement gives a novel interpretation of the columnar to equiaxed transition, and the displacement measurement in different directions within a cast sample reveal the anisotropic character of the volume change.