Microstructural evolution of Al-15Fe alloy produced by mechanical milling and centrifugal atomization

In this study, the Al-15 wt % Fe powders were prepared using two methods: (1) milling of the initial alloy in a ball or a planetary mill; (2) centrifugal atomization. The effect of milling time and distribution of temperature field during atomization on the morphology and microstructure of the Al-15 wt % Fe alloy powders were investigated. After milling, the powders have an agglomerate structure with a size of Al13Fe4 about 4.1-5.4 mu m. Using centrifugal atomization at a blades rotation speed of 2800 rpm resulted in a microstructure consisting of alpha-Al-matrix, stable Al13Fe4 (10-15 mu m) and random oriented short fibres of metastable Al6Fe (2.3 +/- 2.2 mu m). Randomly oriented fibres are formed due to deformation processes that act on the particles during cooling and crystallization. The formation of the metastable Al6Fe is associated with a high cooling rate of nearly 10(6)-10(8) ?/min. The influence of the particle shape on the temperature field was simulated. The stable Al13Fe4 occurs in the centre of the powders according to the low solidification velocity. The crystallization of a uniform structure is possible for particles of regular shape. The matrix of the atomized powder has a cellular microstructure, which introduces an additional reinforcing effect to the Al-15 wt % Fe alloy.