Relation of Critically Refracted Longitudinal Wave (LCR) Velocity with Graphite Nodularity and Matrix in Ductile Iron

The results of an investigation conducted to study the relation of critically refracted longitudinal wave (L_CR) velocity with graphite nodularity and matrix in ductile iron are reported in this paper. The relation between L_CR velocity and graphite nodularity was studied using as-cast test bars obtained from one foundry. Three groups of test bars of similar nodularity obtained from a second foundry were subjected to heat treatment so as to obtain ferritic matrix in the first group, martensitic matrix in the second and tempered martensitic in the third, to enable the relation of L_CR wave velocity with these matrices to be studied. Also three other test bars from the second foundry were subjected to annealing, normalizing and quenching and grouped with an as cast test bar of similar range of nodularity, to evaluate the residual stress developed in each case. The approach followed in this investigation enabled qualitative assessment of the effects of graphite nodularity, matrix and residual stress on the L_CR velocity in ductile iron.