Formation process, microstructure and mechanical property
of transient liquid phase bonded
aluminium-based metal matrix composite joint①
of transient liquid phase bonded
aluminium-based metal matrix composite joint①
(Key Laboratory of Automobile Materials of Ministry of Education,
School of Materials Science and Engineering, Jilin University, Changchun 130025, China)
School of Materials Science and Engineering, Jilin University, Changchun 130025, China)
Abstract: The formation process, microstructure and mechanical properties of transient liquid phase (TLP) bonded aluminium-based metal matrix composite (MMC) joint with copper interlayer were investigated. The formation process of the TLP joint comprises a number of stages: plastic deformation and solid diffusion (stage 1), dissolution of interlayer and base metal (stage 2), isothermal solidification (stage 3) and homogenization (stage 4). The microstructure of the joint depends on the joint formation process (distinct stages). The plastic deformation and solid diffusion in stage 1 favoure the intimate contact at interfaces and liquid layer formation. The microstructure of joint consists of aluminium solid solution, alumina particle, Al2Cu and MgAl2O4compounds in stage 2. The most pronounced feature of joint microstructure in stage 3 is the alumina particle segregation in the center of the joint. The increase of joint shear strength with increasing bonding temperature is mainly attributed to improving the fluidity and wettability of liquid phase and decreasing the amount of Al2Cu brittle phase in the joint. The principal reason of higher bonding temperature (>600℃) resulting in lowering obviously the joint shear strength is the widening of alumina particle segregation region that acts as a preferential site for failure. The increase of joint shear strength with increasing holding time is mainly associated with decreasing the amount of Al2Cu brittle phase and promoting homogenization of joint.
Key words: metal matrix composite; transient liquid phase bonding; microstructure; mechanical properties