Reinforcement of metal alloys with quasicrystalline (QC) particles is a promising approach to creating new materials with improved mechanical properties. Quasicrystals, having a unique atomic structure, combine high hardness, low friction coefficient and good thermal stability, which makes them ideal reinforcing components for aluminum matrices. This work is devoted to the study of the synthesis and mechanical properties of cast aluminum alloys reinforced with QC phases.
The sand casting method was used to obtain reinforced alloys. Aluminum alloys of the AK9ch and AK12 grades were used as a matrix, and the reinforcing phase was CC particles obtained by mechanical alloying. The casting process was carried out in a controlled atmosphere to prevent oxidation of aluminum and CC particles. An important step was to ensure uniform distribution of CC particles in the aluminum matrix to achieve optimal mechanical properties.
This paper describes the production processes and mechanical properties of aluminum-based composite materials in which quasicrystalline particles act as a reinforcing component. Bulk samples of Al–Mn–Ce/Fe and Al–Mn–Pd alloys were produced by die casting in a copper mold at a controlled cooling rate. For comparison and analysis of phase formation under rapid cooling conditions, thin tapes were obtained by melt spinning. The microstructure, strength properties, and deformation behavior of the alloys were studied using X-ray diffraction, scanning and transmission electron microscopy, and calorimetry. Significant differences in phase formation, composite microstructure, and thermal stability of the microstructure were revealed for different compositions. Compression tests at room temperature with a constant strain rate showed that the obtained alloys have improved mechanical properties compared to traditional aluminum alloys. The mechanical properties vary depending on the volume fraction and morphology of the reinforcing particles. Preliminary tests at elevated temperatures have shown promising high temperature stability of the composite.
In recent decades, research efforts have focused on developing new lightweight structural materials. In this regard, aluminum-based alloys, as well as magnesium and titanium, have gained importance for modern structures. Along with the development of alloys based on traditional strengthening mechanisms, such as precipitation hardening, increasing attention is being paid to composite materials reinforced with particles or fibers. The use of ceramics as a reinforcing component allows achieving outstanding strength characteristics. However, an increase in the rigidity of the material is often accompanied by a decrease in ductility. Also, to improve stability at high temperatures, intermetallic phases are used as a strengthening phase in eutectic alloys and precipitation-hardening alloys.
Quasicrystals were first used as a strengthening phase in 1987. In 1989, the first attempt to commercially use quasicrystals in martensitic steel was made. In 1992, strengthening of aluminum alloys using phases with aperiodic structure was successful. Tapes of Al–Mn–Ce melt had a tensile strength of more than 1 GPa. Subsequently, this concept was extended to other alloy systems. Since the application of tapes obtained by melt spinning is limited, research was carried out on the creation of bulk samples.
In this paper, copper mold casting is considered as an alternative method for producing bulk Al-quasicrystal composites directly during solidification. The Al–Mn–Ce/Fe compositions were chosen based on the results obtained by other researchers. The aim of the work is to study the effect of a lower quenching rate on the microstructure and mechanical properties. Melt spinning experiments were also conducted.
Studies have shown that adding CC particles to an aluminum matrix leads to a significant increase in the strength and hardness of the alloy. Thus, the tensile strength of reinforced alloys increased by 20-30% compared to unreinforced analogs. In addition, an increase in microhardness and wear resistance was observed. Microstructure analysis revealed that CC particles effectively prevent crack propagation, which contributes to an increase in fracture toughness.
The results of the conducted studies demonstrate the prospects of using QC particles for reinforcing cast aluminum alloys. The resulting composite materials have improved mechanical properties, which opens up opportunities for their use in various fields of technology, including aviation, automotive and mechanical engineering.
Author: F Schurack, J Eckert, L Schultz
Institute: Institute of Metallic Materials, IFW Dresden, PO Box 27 00 16, D-01171 Dresden, Germany