Microstructure Hierarchy - Mechanical Property Relationship for Hypereutectic Al-Si Alloy Powders Solidified Far From Equilibrium

摘要

Microstructural selection in aluminum silicon powder alloys can directly influence the consolidated materials' mechanical properties. However, due to processing and characterization difficulties, a complete understanding of powder microstructure as a function of undercooling and solidification velocity, and the role microstructure plays on mechanical properties, remains an elusive goal. In this study high pressure gas atomization processing was used to produce rapidly solidified hypereutectic Al-Si alloys. Scanning and transmission electron microscopy have been used to determine the hierarchy of different microstructures. Four different microstructure types, namely, microcellular, dendritic aluminum, coupled eutectic, and primary silicon, have been observed at different undercoolings. Warm extrusion of closely-grouped particle sizes where a given microstructure type dominated was used to generate nearly full density consolidated samples that were machined to tensile specimens. The results of tensile strength measurements are reported for these samples. This work was supported by the US Department of Energy, Basic Energy Sciences under contract no. W-7405-ENG-82.