Direct Brazing of Al/Al2O3 without Wettability of Molten Metal

Al2O3 cannot be directly brazed with aluminum due to the poor wettability of aluminum on alumina below 850 degrees C. Based upon effect of sputtered aluminum wetting on Al2O3, a direct brazing method was proposed to utilize sputtered Al-based films as brazing fillers on alumina. The results show that direct brazing of Al2O3 by Al and Al-Cu alloy can be achieved at 680 degrees C in vacuum with vacuum level only of 0.1 Pa. Through this method, the shear strength of joint with pure Al as brazing filler is 115 MPa and that with Al-1.6at% Cu is up to 163 MPa. When the Cu content in the Al-Cu alloy increases to 14.3at%, the shear strength of joint decreases to 127 MPa, due to the joint fracture generating at the interface caused by the interfacial segregation of Cu. Moreover, the principle of this direct brazing method not based on wettability of molten metal is analyzed.