Effect of Joining Conditions on the Shear Strength of Barium Titanate Joint Brazed with Molten Aluminum

Abstract

The shear tests using barium titanate joint brazed with molten aluminum under several joining conditions were conducted to determine the optimum joining condition. The barium titanate joints brazed at 780℃ had estimative strength, while those brazed at 720℃ did not. The strengths of the joints brazed at 780℃ became higher with increase in the heat holding time. Especially, the heat holding time for more than 24 h gave higher joint strength than the original shear strength of barium titanate. To discuss the bonding mechanism, the fractured surfaces of the joints were observed and the cross-sectional element distributions in the vicinity of the joint interface were investigated. The observations demonstrated that pieces and grains of the fractured barium titanate were strongly bonded to the aluminum layer at longer holding times. Meanwhile, from the oxygen distributions, relatively thick alumina layers that formed between barium titanate and aluminum at longer holding times were observed. These facts suggest that interfacial bonding is achieved through the formation of an alumina interlayer due to progressive oxidation of molten aluminum during joining process.