Microstructure and synthesis mechanism of Al-Ti-C-Sr master alloy

Al-5Ti-0.5C-8Sr (mass fraction, %) master alloy was prepared using a melt reaction method. The microstructure and synthetic process of the master alloy were investigated by optical microscopy, X-ray diffraction, scanning electron microscopy and X-ray energy-dispersive spectrum. The results show that the master alloy is composed of a(Al), TiAl₃, TiC, Al₄Sr and Al-Ti-Sr phases. The synthesis mechanisms of the master alloy are as follows: TiAl₃ is formed through the reaction between K₂TiF₆ and Al melt at 850 °C; when the melt was heated up to 1 200-1 300 °C, TiC was formed through the reaction: Ti+C(s)=TiC(s); Al₄Sr was formed through the binary uniform reaction when Sr was added into the melt; after the following solidification process in the peritectic reaction: L(Al, Sr)+α(TiAl₃)→β(Al-Ti-Sr), the enwrapped structure was formed with the outer layer of Al-Ti-Sr phase and the internal layer of TiAl₃ phase.