Reaction mechanisms between Al and Fe_3O_4powders in theformation of an Al-based metal matrix composite

摘要

The reaction mechanisms between Al and Fe_3O_4powders were investi-gated. Differential thermal analysis revealed that a two-step displacementreaction between Al and Fe_3O_4took place during sintering. Initially, theFe_3O_4was converted to amorphous FeO at～720°C and some of the Al wasoxidized to amorphous Al_2O_3. In the final stage, when temperaturereached ～840°C, crystalline Al_2O_3particles were produced in the moltenAl-Fe liquid. The effects of cooling rate on the microstructures werestudied. When the Al-Fe liquid was furnace-cooled to room temperature,proeutectic Al_3Fe plates, plate-like divorced eutectic Al_and 2O_3particles were in situ formed in the Al(Fe) matrix. While quenching from700°C, nanometer-sized Al dendrites and Al-Al_6Fe eutectic lamellae wereproduced in the Al matrix. However, when it was rapidly quenched from900°C, the size of the proeutectic Al_3Fe phases was further reduced andAl_6Fe nanorods were found in the Al-Al_eutectics. A model wasproposed to describe the transformation of the Al-Fe intermetallics duringsolidification.