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.
Highlights
The development of high-strength Al-based composites is proceeding with great intensity worldwide today
Aluminum matrix composites reinforced with recycled Cu-Zr-based nanocrystalline particles were synthesized by the powder metallurgy route
The CuZrAgAl reinforcement with Al3 Zr shell uniformly distributes in the Al matrix
Summary
The development of high-strength Al-based composites is proceeding with great intensity worldwide today. Intermetallic precipitates in the matrix are more favorable for high-strength Al-based alloys at elevated temperatures [4,5,6]. 4 (Ti [9,10], Zr [11,12]) transition metals are promising alloying elements for heat resistant Al alloys. Zr seems to be the most promising alloying element for high temperature use [11,13,14,15]. The solid solubility of this transition element in Al is very limited and the diffusion is very slow in the Al matrix. In the case of Zr, the maximum solubility limit of Zr in Al at 656 ◦ C is only 0.07 at.% [16], and this limit reduces in proportion to the decrease in temperature
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