In modern industry, aluminum-based alloys have become widespread due to their favorable mechanical properties. However, their use is limited by a high coefficient of thermal expansion, especially at elevated temperatures. In this regard, the development of new aluminum alloys that demonstrate a low coefficient of expansion when heated is relevant.
The introduction of small additions of cerium into the Al-Cu-Fe alloy has a significant effect on its microstructure and thermal properties. Cerium, being a rare earth element, modifies the alloy structure by refining the grain and changing the morphology of the intermetallic phases. This leads to an increase in mechanical properties such as strength and ductility.
Various ceramic particles (oxides, carbides, nitrides) were previously used as reinforcing elements for the aluminum matrix. Unfortunately, weak adhesion between aluminum and ceramics leads to the formation of defects at the interface, which become stress concentrators and promote crack propagation. Recently, interest in aluminum alloys reinforced with a quasi-crystalline phase has increased due to their improved mechanical properties and stability at high temperatures.
The discovery of icosahedral quasicrystals was made by Shechtman, who opened up a new field of research. These structures are characterized by forbidden symmetries and long-range orientational order. The discovery and potential of quasicrystalline alloys stimulated considerable research interest and demonstrated the prospects for their application.
The Al-Cu-Fe system is one of the first in which the formation of a stable icosahedral phase was detected. However, Al-Cu-Fe alloys are generally highly brittle.
The properties of the Al-Cu-Fe alloy depend largely on the type and amount of alloying elements. Additions of boron, silicon, magnesium, tin, cobalt, and chromium can change the brittleness and improve the strength of the icosahedral phase. The effect of chromium and nickel has also been studied: chromium increases thermal stability, and nickel improves the microstructure.
Cerium is known for its ability to refine grain in aluminum alloys, improving their mechanical properties and thermal stability.
The addition of cerium also affects the coefficient of thermal expansion (CTE) of the alloy. Depending on the concentration of cerium, the CTE can either decrease or increase. This is due to the fact that cerium forms new intermetallic compounds with aluminum, copper, and iron, which have different thermal properties than the original phases.
Optimization of the cerium content allows us to obtain an Al-Cu-Fe alloy with improved characteristics, which expands the possibilities of its application in various fields of technology where a combination of high strength and dimensional stability at elevated temperatures is required.
Author: Huan Wang, Zhong Yang, Zhijun Ma, Hongbo Duan, Jiachen Zhang, Dong Tao and Jianping Li
Institute: School of Materials Science and Chemical Engineering, Xi’an University of Technology, Xi’an 710021, People’s Republic of China