Microstructure and properties of metal matrix compositel/stainless steel friction joints containing silver interlayers

Abstract

The influence of a silver interlayer and friction joining parameters on the microstructure and mechanical properties of friction joints between aluminium based metal matrix composite (MMC) and AISI 304 stainless steel substrates is investigated. The highest notch tensile strength properties were obtained in MMC/Ag/304 stainless steel and MMC/304 stainless steel joints produced using high friction pressure. The introduction of silver during MMC/304 stainless steel friction joining promoted the formation of a veined microstructure containing a mixture of silver, an intermetallic phase, and entrained Al₂0₃ (the intermixed region). A second microstructure, the plastic deformed region, consisted of a fine grained dynamically recrystallised MMC matrix including granular silver, Ag₃Al, and reinforcing particles. The intermetallic Ag₃Al formed as a result of mechanical mixing very early in the friction joining operation. The beneficial effect of using high friction pressure during friction joining was related to the formation and retention of microstructures containing Ag₃Al.