Effect of Si and Holding Time on Ti₂Al₂₀La Phase in Al-Ti-La Intermediate Alloy

The effects of holding time and Si on the content, shape size and structure of Ti₂Al₂₀La phase in Al-Ti-La intermediate alloy were investigated by an X-ray diffractometer, scanning electron microscope and transmission electron microscope. The results show that the volume fraction and aspect ratio of Ti₂Al₂₀La phase in Al-Ti-La intermediate alloy decrease significantly, from 21% and 2.3 without Si addition to 4% and 2.0 with the addition of 2.3 wt.% Si at a holding time of 15 min at 750 °C, respectively. The Si element will attach to the Ti₂Al₂₀La phase and form La-Si binary phase at the grain boundary of α-Al. With the increase of holding time from 15 min to 60 min, the content of Ti₂Al₂₀La phase in the alloy gradually decreases and the size decreases significantly. Meanwhile, Al₁₁La₃ will dissolve and disappear, while the content of La-Si binary phase increases, and part of Ti₂Al₂₀La phase transforms into Ti₂(Al_20-,Si)La phase.