Comparison of Absorption and Desorption of Cryomill Process Control Agents and Their Effect on Compressive Behavior of Trimodal Aluminum Metal-Matrix-Composites

Aluminum composite (AA5083) and boron carbide (B4C) powders were cryomilled in liquid nitrogen using different process control agents (PCAs) such as oleic acid, caprylic acid, and stearic acid individually in order to determine the effect of each PCA on the resultant microstructure and mechanical properties. The microstructure of the powders was examined and consolidated samples were mechanically tested in compression. Chemical analysis was performed to determine impurity concentrations of nitrogen, hydrogen, and oxygen. Microstructural analysis of the powders revealed three types of agglomerates: composite powders of AA5083 with uniformly distributed B4C particulate, unmilled spherical AA5083 powder and deformed AA5083 powder. These three types of agglomerates were found in similar size and proportion regardless of the PCA used. Correlation among PCA type, impurity concentrations, microstructure, and mechanical properties were examined. The original document contains color images. Prepared in collaboration with Bowhead Science and Technology, Belcamp, MD, the University of Central Florida, Orlando, FL, Oak Ridge Institute for Science and Education, Belcamp, MD, and Pittsburgh Materials Technology, Jefferson Hills, PA.