Microstructure of Al-Ti-B-Er refiner and its grain refining performance

Al-Ti-B-Er refiner was successfully prepared by CR (contact reaction process), a process based on SHS (self propagating high-temperature synthesis). The microstructure of the alloy was studied by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry. The results showed that Al-Ti-B-Er alloy was composed of alpha-Al, block-like TiAl3 and flocked TiB2. Compared with Al-Ti-B refiner, formation of TiAlEr compounds, Er modified the morphology of TiAl3 phase, and dispersed the TiB2 and TiAl3. An excellent grain refining performance was obtained when adding 1 wt.% Al-Ti-B-Er in Al-10Zn-1.9Mg-1.6Cu-0.12Zr alloy, the average grain size was about 40 mu m. The refinement mechanism of Al-Ti-B-Er was also discussed. Er changed the morphology of TiAl3, TiB2 phase, the refiner would be more efficient. The decomposition of TiAlEr compounds which released Er refrained the growth of TiAl3 and made TiB2 difficult to aggregate or deposit, therefore resulted in more particles being efficient nucleation substrate.