Microstructure Evolution of Al/Fe Liquid/Solid Interface

Abstract

The liquid/solid composite technology has wide range of applications in the preparation of Fe-Al composite materials and structures. The diffusion-reaction zone (DRZ) formed in the liquid/solid interface has a great influence on their properties. The Al-Fe diffusion couple was prepared by using the insert technology and treated at 700°C-900°C. The microstructure evolution and growth mechanism of the DRZ in the Al/Fe liquid /solid interface were investigated. The result shows that the microstructure of Al/Fe liquid/solid diffusion couple after heat treatment (HT) is (Al+FeAl3)/FeAl3/Fe2Al5/Fe; Fe2Al5 is the only new phase during the heat preservation process, FeAl3 is formed by desolventizing during the cooling process. The growth of the Fe2Al5 is controlled by the chemical reaction of the Al atoms and Fe atoms before the Fe2Al5 continuous single-phase layer is formed; Once the continuous Fe2Al5 single-phase layer is formed, the growth of the Fe2Al5 mainly depends on the diffusion of Al atoms in the solid phase Fe2Al5 layer, and the reaction occurs in the solid/solid interface of the Fe2Al5 layer and iron. Precipitate is not found in the iron while the needlelike and strip FeAl3 precipitates appear in the aluminum; the density and size of the FeAl3 precipitates decrease gradually from the vicinity of interface to the distant.