Effects of Cu interlayers on the microstructure and mechanical properties of Al₂O₃/AgCuTi/Kovar brazed joints

Abstract

Al2O3 ceramic and Kovar alloy brazed joints were achieved using three types of Ag‐based interlayers: a AgCuTi foil, a AgCuTi/Cu foil/AgCuTi multi‐interlayer and a AgCuTi/Cu foam/AgCuTi multi‐interlayer. The effects of the addition of Cu interlayers on the interfacial microstructure and mechanical properties of Al2O3/AgCuTi/Kovar brazed joints were investigated. When Kovar alloy and Al2O3 ceramic were brazed with 50 μm Cu foil at 900°C for 10 minutes, the Cu foil was completely dissolved in the liquid filler. A nearly continuous Cu layer remained in the joint when the thickness of the Cu foil reached 100 μm under the same brazing conditions. With the increase in Cu foil thickness, the thickness of Ti–O compounds + Ti3Cu3O reaction layer formed nearby the Al2O3 ceramic first increased and then remained the same. The Al2O3/Kovar joints brazed with 100 μm Cu foil at 900°C for 10 minutes showed a maximum shear strength of 138 MPa. A low brazing temperature was beneficial to maintain the original structure of the Cu foam. Furthermore, when the joints were brazed at 880°C for 10 minutes, the average shear strength of the Al2O3/AgCuTi/Cu foam/AgCuTi/Kovar joints was 140 MPa, which was 30 MPa higher than that of a single AgCuTi interlayer.

Enhanced shear strength of Cu/AlN/Cu gradient materials with continuous and quasi‐continuous interfacial structures

“…Therefore, extensive research has been conducted on connections among Cu, AlN, or other ceramic-metal interfaces. 2 Liao et al 3 used a W-Cu composite with a lower coefficient of thermal expansion (CTE) instead of pure Cu to form the joint with AlN, which can prevent mechanical failures at the interface resulting from mismatched CTE between Cu and AlN. The maximum average tensile strength for the joints reached 26.76 MPa at 800 • C. Terasaki et al 4 utilized a kind of Ag-free Cu-P-Sn-Ni brazing alloy with Ti as an active metal addition to joining Cu and AlN.…”

“…The key lies in enhancing the mechanical reliability of the Cu/AlN joint, as the failure usually occurs at Cu/AlN interface. Therefore, extensive research has been conducted on connections among Cu, AlN, or other ceramic–metal interfaces 2 . Liao et al 3 .…”

Effect of Ni foam on the microstructure and properties of AlN ceramic/Cu brazed joint

“…The porous structure of the metal foam layer can absorb fracture energy of the joint 29,30 . Due to the large elastic moduli and suitable CTE, these interlayers can transfer thermal stress from ceramic to the middle layer, which can inhibit the generation of cracks inside the ceramic 31 .…”

Microstructure and mechanical properties of Al2O3 ceramic joints achieved by Ag‐SiO2 braze in air

“…They have been successfully applied in industries, such as aerospace, nuclear, and electronics industries. [1][2][3] For several practical applications, Al 2 O 3 ceramic components with large dimensions or complex geometries are required. 4 However, the intrinsic high hardness and brittleness of Al 2 O 3 cause the ceramic to present poor machinability.…”

“…Alumina (Al 2 O 3 ) ceramics possess superior mechanical properties, such as high strength and hardness, reliable chemical stability, and wear resistance. They have been successfully applied in industries, such as aerospace, nuclear, and electronics industries 1–3 . For several practical applications, Al 2 O 3 ceramic components with large dimensions or complex geometries are required 4 .…”