DEVELOPMENT OF MASTER SINTERING CURVE FOR SPARK PLASMA SINTERING OF 93W-5.6Ni-1.4Fe HEAVY ALLOY

Tungsten heavy alloys are used for a number of applications, including radiation shields, counter weights, electrical contacts, vibration dampeners and kinetic energy penetrators. The most common compositions consist of W along with some combination of Ni, Fe, or Cu. The alloys are usually fabricated by the conventional powder metallurgy technique, in which the elemental blended powders are first compacted and then followed by a high temperature sintering. An important processing goal for this alloy is to obtain a high density with fine grain size. It is therefore desirable to predict its densification behavior and final density. Recently, the master sintering curve (MSC) theory provides a better understanding of whole sintering process. In previous work, the densification and grain growth mechanisms during spark plasma sintering (SPS) of 93W-5.6Ni-1.4Fe heavy alloy were investigated. In this investigation, the master sintering curve approach was first extended theoretically to spark plasma sintering of 93W-5.6Ni-1.4Fe heavy alloy. Two master sintering curves of 93W-5.6Ni-1.4Fe heavy alloy in different heating rate stages (with heating rate of 100 degrees C/min as division point) during SPS process were developed. Both of the master sintering curves can effectively predict the densification behavior of 93W-5.6Ni-1.4Fe heavy alloy during SPS process, as well as the shrinkage and final density. The calculated densification function c quantitatively shows that the densification process increases with temperature when heating rate is higher than 100 degrees C/min. In addition, the apparent densification activation energies calculated by MSC are roughly identical to those obtained by Arrhenius method.