Fabrication of Al-Mg in situ nanocomposites via friction stir processing

Aluminum based in situ nanocomposites were fabricated via friction stir processing (FSP) of an aluminum-copper (AA2024) alloy with pre-placed magnesium powder in the stirred zone. Microstructural evolutions and formation of intermetallic phases were analyzed by optical and electron microscopic techniques across the thickness section of the processed sheets. The microstructure of the nanocomposite consisted of a fine-grained aluminum matrix (6-7 µm), and reinforcement particles of Al3Mg2 and Al12Mg17 without any unreacted magnesium powder. Detailed microstructural analysis indicated solid-state interfacial reactions between the aluminum matrix and micro-sized magnesium particles to form intermetallic phases. The hard inclusions were then fractured and re-distributed in the metal matrix by the severe thermo-mechanical conditions imposed by FSP. Evaluation of hardness measurements determined significant enhancement in the mechanical strength (by 2 order of magnetite). Based on a dislocation-based model analysis, it was suggested that the strength enhancement was governed by grain refinement and the presence of hard inclusions in the metal matrix.

کلیدواژه ها:

Friction stir processing ، in-situ nanocomposite ، intermetallic compounds