Mechanism Of Interfaces Formation Of Aluminum Based Filler Metal On Sapphire Ultrasonic Aided Brazing

In order to meet the requirement of sapphire/metal joints, a method at a lowtemperature is explored.Brazing of sapphire to TC4alloy was carried out usingAl-12Si alloy filler metal and7050aluminum alloy filler metal. Themicrostructure and properties of the joints were discussed by means ofexperimental examination and theoretical analysis. The main purpose of this studyis to analysis the bonding mechanism how interfaces connect with each other andmechanical properties of the joints. The effect of different brazing parameters onthe interfacial microstructure and properties of the joints was studied．The results indicated that the brazing of sapphire to TC4alloy was realizedusing Al-12Si alloy filler metal and7050aluminum alloy filler metal underoptimal brazing parameters. Al-12Si alloy filler metal was used to investigate thejoining mechanism and interface structure between sapphire and TC4alloy whenthe brazing temperature was620℃, the ultrasonic time is10s, the joining pressurewas2MPa, and the vibration amplitude of ultrasonic was10μm. It is found that,when Al-12Si alloy is used as filler metal, sapphire join with filler metal with anepitaxial growth Al₂O₃layer on interfaces. It’s confirmed that the epitaxial growthAl₂O₃layer is amorphous by TEM, and the epitaxial growth amorphous Al₂O₃layer is20nm thick. The interface structure is sapphire/Al₂O₃amorphous/Al-12Si.Al₂O₃layers on interfaces were incomplete and unreacted areas existed whenultrasonic aided brazing technology was not employed or employed too short timesuch as4s. Interfaces were complete covered by Al₂O₃when ultrasonic aidedbrazing technology was employed10s or longer time. What’s more, the longertime ultrasonic aided brazing technology was employed, the thicker the Al₂O₃layers would be. When the ultrasonic aided brazing technology was employed10sto300s, shear strength of the joints was60.74-65.15MPa. The joints cracked at theinterfaces of Si and Al₂O₃.7050aluminum alloy filler metal was used to investigate the joiningmechanism and interface structure between the sapphire and TC4alloy when thebrazing temperature was680℃. It is found that, when7050aluminum is used asfiller metal, sapphire join with filler metal with an epitaxial growth Al₂O₃oninterfaces as well.Without Si, the sheer strength of the joints was improved to84.1MPa. The joints cracked at the interfaces of Al and Al₂O₃.