Microstructure and property of bonds obtained by vacuum brazing using Al-Si-Ti-Cu-In filler metal

Aluminium matrix composites with 70% volume fractions of SiC particles, as the reinforcements, were brazed in the vacuum furnace using Al-Si-Ti-Cu-In alloy as filler metal. The microstructure and constituent of the joints were examined by means of SEM and EDS. Meanwhile, welded joints were submitted to shear test. The result shows that high quality joints were acquired, which mainly contains honeycomb Al base phase, Ti, In rich phase and annular Si rich phase. The brazing process sincludes five stages: (1) particles cohere; (2) liquid flows and particles rearrange; (3) the sintering neck grows; (4) second liquid flows and pores fill; (5) closed pores englobe and narrow. The reducing of the sintering body’s and pores’ free surface energy drove the sintering process to continue. The maximum shear strength was 90 MPa. The fracture belongs to mixing fracture with the characteristic of both the cleavage fracture and the micro void accumulation fracture.