Development of Al-12Si-xTi system active ternary filler metals for Al metal matrix composites

To improve the wettability of Al metal matrix composites (Al-MMCs) by common filler metals, Al-12Si-xTi (x=0.1, 0.5, 1, 3.0; mass fraction, %) system active ternary filler metals were prepared. It was demonstrated that although the added Ti existed within Ti(Al1-xSix)3 (0≤x≤0.15) phase, the shear strength and shear fracture surface of the developed Al-12Si-xTi brazes were quite similar to those of traditional Al-12Si braze due to the presence of similar microstructure of Al-Si eutectic microstructure with large volume fraction. So, small Ti addition (∼1%) did not make the active brazes brittle and hard compared with the conventional Al-12Si braze. The measured melting range of each Al-12Si-xTi foil was very similar, i.e., 580-590 °C, because the composition was close to that of eutectic. For wettability improvement, with increasing Ti content, the interfacial gap between the Al2O3 reinforcement and filler metal (R/M) could be eliminated, and the amount of the remainder of the active fillers on the composite substrate decreased after sessile drop test at 610 °C for 30 min. So, the wettability improvement became easy to observe repeatedly with increasing Ti content. Additionally, the amount and size of Ti(AlSi)3 phase were sensitive to the Ti content (before brazing) and Si content (after brazing).