Instability of TiC and TiAl₃ compounds in Al-10Mg and Al-5Cu alloys by addition of Al-Ti-C master alloy

The performance of Al-Ti-C master alloy in refining Al-10Mg and Al-5Cu alloys was studied by using electron probe micro-analyzer (EPMA) and X-ray diffractometer (XRD) analysis. The results indicate that there are obvious fading phenomena in both Al-10Mg and Al-5Cu alloys with the addition of Al-5Ti-0.4C refiner which contains TiC and TiAl₃ compounds. Mg element has no influence on the stability of TiC and TiAl₃, while TiC particles in Al-10Mg alloy react with Al to form Al₄C₃ particles, resulting in the refinement fading. However, TiC particles are relatively stable in Al-5Cu alloy, while TiAl₃ phase reacts with Al₂Cu to produce a new phase Ti(Al, Cu)₂, which is responsible for the refinement fading in Al-5Cu alloy. These indicate that the refinement fading will not occur only when both the TiC particles and TiAl₃ compound of Al-Ti-C refiner are stable in Al alloys.