Effect of Process Control Agent on the Microstructure and Mechanical Behavior of an Aluminum and B₄C Metal Matrix Composite

Abstract

AA5083 and B4C powders were cryomilled in liquid nitrogen utilizing oleic, caprylic and stearic acids individually in order to determine the effect of each process control agent 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, un-milled spherical AA5083 powder and deformed AA5083 powder. These three types of agglomerates were found in similar size and proportion regardless of the process control agent used. Nitrogen concentration correlates directly to the oxygen concentration in the sample. There was a slight increase in compressive strength with the increase in oxygen and nitrogen concentrations.

Nanostructuring of Aluminum Alloy Powders by Cryogenic Attrition with Hydrogen-Free Process Control Agent

“…Recently we have explored using various PCAs and studied their effect on the mechanical response of trimodal Al metal matrix composites. 5 Most of the PCAs commonly used (e.g., stearic acid, oleic acid, caprylic acid) contain carbon and hydrogen (H). It is important to have as little H as possible in the structural material to avoid brittleness.…”