Understanding the impact of high-energy ball mill tooling on powder refinement and alloy formation: Microstructural evolution in immiscible W-Cr alloys

High-energy ball milling provides an effective means to drive thermodynamically non-favorable solid solutions while also refining the microstructure of powders. Key parameters in this process, such as the size and hardness of the milling media, the hardness of the milling vessel, and the ball-to-powder ratio, can have a major effect on the resultant powders. Using W-10 wt.% Cr as a model system, we establish the relationship between processing/tooling parameters and the resultant powders. Here, we find that the larger milling media provides higher energy per collision, enabling further crystallite refinement but limiting the total frequency of solute-dissolving impacts. Additionally, we find that variation between the first and subsequent milling runs is not significant, indicating negligible “seasoning” effects from prior use of the milling vessel for the reported material system. These findings provide insight into the role of processing parameters in tailoring the microstructure of immiscible and refractory alloys, with implications for extrapolation to the ball milling of a wide range of material systems.