The effects of co-injection of ceramic particulates on the microstructural evolution and mechanical properties of aluminum based metal matrix composites processed using spray atomization and deposition

In the present study spray atomization and deposition technique has been utilized to process metal matrix composites. Theoretical studies were carried out to characterize the mass flow rates of ceramic particulates during coinjection for different injection pressures and the volumes of fluidized bed injectors. Experimental results obtained were consistent with the theoretical results.; Metal matrix composites processed using spray atomization and deposition were subsequently characterized for microstructural evolution. The microstructural features observed in metal matrix composite samples were compared to their monolithic counterparts. The refined microstructure observed in the as-spray deposited composites samples was correlated with the solidification effects, heat transfer effects, and grain boundary pinning effects brought about as a result of the presence of ceramic particulates in the matrix. The results of numerical model formulated to quantify the heat transfer brought about by the presence of ceramic particulates were consistent with the experimental observations.; Another interesting feature associated with spray deposited metal matrix composites was the nature and characteristics of the distribution of ceramic particulates in the matrix. This was explained using the existing particulate engulfment/rejection models. In addition, mechanically driven engulfment criterion was proposed to explain the presence of SiC particulates inside the grains.; The results of the interface studies showed the presence of a segregation profile of the solute as a function of the distance from the interface. Interfacial reaction products were not observed irrespective of the chemistry of the alloys used in the present study. In addition, a new concept of dynamic wettability was introduced to explain the good interfacial bonding observed between the SiC particulates and Al-Li matrix.; Finally, the results of mechanical properties characterization conducted on a commercial Al-Cu alloy (2519 designation) suggested that a critical volume fraction of ceramic particulates is required in order to realize an improvement in strength of metal matrix composites. A numerical model was formulated to develop an expression for the critical volume fraction of equiaxed reinforcement necessary to realize the strength improvement in metal matrix composites processed using spray atomization and deposition. The theoretical results exhibited excellent agreement with the experimental findings.