Availability of in-situ reinforced active-transient liquid phase bond with good Wettability for 70 vol.% SiCp/A356 composite using Al-Mg-Ga-Ti interlayer

For transient liquid phase bonding of as-cast 70 vol.% SiCp/A356 composite, Al-24Mg-16Ga-1Ti (wt.%) active braze was designed by adding Ti as melting point increaser (MPI) for Al into Al-Mg-Ga active alloy near eutectic composition to produce in-situ reinforcement by precipitating a fine and dispersive Ti-containing intermetallic compound as reinforcement within the solid-solution bond seam after isothermal solidification. Bonding was performed at three temperature levels of quasi-melting (450 degrees C), just fully melting (500 degrees C), and over melting (550 degrees C) for the braze under 0.5-1.75 MPa in argon. The braze was able to produce fine (less than 1 mu m) and dispersive Ti-containing precipitated phase (Al-2Mg-1Ga-0.5Ti, at.%) as in-situ reinforcement only at 500 degrees C under medium pressure (1-15 MPa), increasing bond seam microhardness by 30 Hv over the matrix. The braze robustly showed good wettability for each temperature due to the matrix dissolution and detectable amorphous reaction products containing Mg and Ga on SiC surface. Higher temperature caused coarsening of needle-like Si containing Al-Si-Ti precipitated phase while higher pressure produced blocky Al3Ti with a shell of Mg and Ga. Sound joint produced at 500 degrees C under 1.5 MPa with 118.6 MPa shear strength (98.8% parent composite) fractured completely within the composite. (C) 2016 Elsevier Ltd. All rights reserved.