Quenching Behavior and Process Optimization of Cast Binary Uranium Alloy

The depleted uranium 6-weight percent niobium (dU-6wt% Nb) alloy is of key interest to researchers at both the Department of Defense and the Department of Energy. One of the primary processing methods for dU-6wt%Nb is foundry casting which results in a dual-phase microstructure. Subsequent application of a homogenization heat treatment with a minimum quench rate of 20 °C/s is required to achieve the desired single-phase monoclinic-α’’ microstructure. Restricted ability to process this material have resulted in a lack of data regarding the thermal history during heat treatment and quenching, which is further complicated by a difficult to instrument, dual-chamber, vacuum, oil quench furnace. This investigation seeks to develop a methodology for characterization of through-thickness quench rates in cast geometries following homogenization heat treatments. As part of this work, several instrumented quenching trials were conducted on dU-6wt%Nb cast cylinders. From these data, variations in quench rate related to casting size and geometry, furnace load, and load configuration were documented. This work is expected to facilitate a discussion of manufacturing process and material property optimization which may be of particular interest to those who work with heat treatment systems that are challenging to instrument or unusual alloy systems with limited literature availability.