Qualitative Identification of phases of Al-1.5 wt.% Fe treated by laser surface remelting by means of grazing incidence X-ray diffraction

ABSTRACT

There are currently an extensive research on aluminum alloys, mainly due to its wide application in the automo-tive and aerospace industry, due to its characteristics, such as, low density, high thermal and eletric conductivity and high corrosion resistance at room temperature. Fe-Al alloys have a high degree of modification of their mi-crostructure when used an appropriate treatment, consequently to improve their properties. In this work, the study sample was Al-1.5 wt.% Fe alloy treated through laser superficial remelting (LSR) in order to improve its surface characteristics. The identification of this alloy, with respect the present phases, was performed by means of grazing incidence X-ray diffraction (GIXRD) as a function of depth. In this technique, the angle incidence of X-rays is fixed, and the scanning 2θ detected by detector, in order to obtain diffraction patterns at different depths varying only the angle of incidence. The analysis was performed in micrometer scale in two different collections DRXIR data. First, the angle of incidence was varied from 0.5° to 6°, at intervals of 0.5° in continuous scan mode from 20° to 90°. The second, with incidence angles of 3° and 6°, for step scan mode at 20° to 120°, used to improve the quality of diffraction patterns, and hence improve the identification phase. As a result, characterization of the microstructure of the surface treated by the technique LSR, as well as the cross section of the treated layer by SEM and light microscopy and energy dispersive spectroscopy (EDS) was made, furthermore, to the application of the technique GIXRD, phase profile as a function of depth in a layer 0.6 to 7.8 µm were obtained, metastable phases, such as AlN, Al₂O₃ and Al_2.144O_3.2, and simple phase, as Al and Fe were identified in consequence of the high cooling speed and the treatment was conducted in the atmospheric environment.

Keywords:
GIXRD; microstructural characterization; Al-Fe alloys; aluminum oxide and AlN