In-situ aluminum 7075 metal matrix composites development for additive friction stir deposition

Abstract

Al7075 equivalent aluminum + Al₂O₃ metal matrix composite (G7D) feedstock tailored for Additive Friction Stir Deposition (AFSD) was successfully produced using the powder metallurgy and hot extrusion process. Two types of feedstocks with different densities, categorized as High Porosity (HP) and Low Porosity (LP) rods, were AFSD deposited to evaluate their performances. High-quality and fully dense AFSD samples were successfully deposited using both HP and LP rods. The microstructure, grain size distribution, and hardness were evaluated in the as-deposited AFSD samples. The deposited G7D exhibited complex material flow, but deposition parameters had minimal impacts on the flow patterns. During the AFSD process, ceramic particles (Al₂O₃) were evenly dispersed in the matrix. The use of elemental powders rather than pre-alloyed powders allows the low-melting-point metal Zn in the powder mix to form a liquid-phase diffusion pathway during hot extrusion/AFSD, improving the wettability of Al₂O₃ particle surfaces and significantly strengthening the connection between the aluminum matrix and the Al₂O₃ particles. It shows the significant potential of AFSD in fabricating Aluminum Metal Matrix Composites (AMMC) for producing high-quality AMMC components with comparable or superior performance to those made by conventional methods.