Hot-rolled Zn22Al2Cu-NaCl composite with initial fine-grained and cast-metal matrix microstructures

Abstract

A composite of a Zn22Al22Cu matrix and NaCl particles was developed to establish whether this material could be hot-rolled and, if feasible, to determine the structural changes according to the initial matrix microstructure and percent section reduction achieved with this process. The composite was made by melting the alloy, adding the particles, molding, compressing the mixture of metal and particles, and air cooling, with an approximate (mass of particles)/(mass of alloy) ratio equal to 0.6. Plates of the composite with the initial cast-metal matrix microstructure and with a heat-treated initial fine-grained matrix microstructure were hot-rolled in two stages to approximately 80% section reduction at 230◦C. Plate samples that were not rolled, plates hot-rolled to approximately 50% section reduction and plates hot-rolled to the maximum percent reduction were mirror-polished, and the matrix and NaCl-particle interfaces were analyzed and imaged with a scanning electron microscope. Vickers microhardness was measured in the matrix and in NaCl particles, and Rockwell hardness F of the nonrolled and hot-rolled composites was determined. The cast-metal matrix microstructure acquired shape texture without recrystallization, while the finegrained matrix microstructure recrystallized with increasing rolling %. The NaCl particles deformed together with the matrix and hardened, with the hardening speed being greater when the matrix was fine-grained. The composite could be hot-rolled with either microstructure, with the cast-metal matrix microstructure being more favorable. The hot-rolling of this material allows the production of thin cellular sheets to be obtained.