Effect of heat treatment parameters on hardness variation of ADI studied by factorially designing the experiments

ADI is a well-established engineering material. Although the excellent mech anical properties achievable in ADI have been reported since 1950's, the co mmercial exploitation has been delayed because of the careful control that must be exercised over alloy content, solidification microstructure and hea t treatment variables to obtain the unique microstructure responsible for o ptimum properties. The aim of the present study is to determine a quantitat ive relationship between hardness and various heat treatment parameters for an ADI with the following composition: C-3.65%, Si-2.45%, Mn-0.35%, Cu-0.4 0%, Cr-0.05%, Sn-0.02%. Factorial design of experiments has been applied to plan the experimental procedure. Linear equations connecting hardness with heat treatment parameters has been derived both in the upper as well as lo wer ausferritic regions. It may be noted that there exists a linear relatio nship (inverse) between Re hardness and endurance limit, An attempt has bee n made to find possible explanation for signs and values of the coefficient s in the equations generated so that some insight into the mechanism of tra nsformation using this statistical tool can be obtained. Processing windows for the above mentioned ADI has been predicted based on the current experi mental results and existing literature.