Strengthening of Nanocrystalline Al with Al3Zr Core-Shell Structure

Abstract

High-density Al-based composites reinforced with ten-wt% recycled nanocrystalline CuZrAgAl particles have been fabricated by mechanical milling, cold- and hot-pressing. The microstructures, phase transformations, and mechanical properties of the mixed powder and sintered samples were investigated. After milling in a ball mill for 30 h, the microhardness of the mixed powder increases to 301 ± 31 HV0.01 and 222 ± 10 HV0.01 without and with ethanol milling, respectively. On account of the interdiffusion, the melting temperature of mixed powder reduces to 574 ± 5.0 °C and 627.5 ± 6.5 °C after 30 h milling. The study showed that the reinforcing particles are homogeneously distributed in the sintered nanocrystalline Al-based composites. During the hot-pressing, a shell zone forms at the interface of reinforcing particles during hot pressing after high energy milling with a minimum of ten hours milling time. This shell zone consists of Al3Zr (D023) phase. The coarsening resistant core-shell structure and grain refinement greatly improve mechanical properties. The compression strength at room temperature varies between 650 and 800 MPa at room temperature and is 380 MPa at 400 °C for the composite containing ten-wt% of the Cu-Zr-based amorphous-nanocrystalline phases. The Brinell hardness of the sintered composite is 329 HB.

143962

“…The effect of this phase on casting properties is still not fully explained. According to the authors of [20,21], this phase inhibits the migration of grain boundaries, taking place in the processes of recrystallization and grain growth, i.e. during heat treatment.…”

143961

“…The effect of this phase on casting properties is still not fully explained. According to the authors of [20,21], this phase inhibits the migration of grain boundaries, taking place in the processes of recrystallization and grain growth, i.e. during heat treatment.…”