Possibility of Strengthening Aluminum Using Low-Symmetry Phases of the Fe-Al Binary System
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MODERN design solutions require lighter and more durable materials. Composites consisting of light metals and other types of materials in various configurations have become increasingly feasible, thus creating new design possibilities. The most commonly known and used light metal is aluminum and its alloys. Pure aluminum is characterized by a low density (2.7 g/ cm3), which is its greatest advantage, and a high elongation value of up to 35 pct. However, it also has poor mechanical properties, such as low hardness (18 HB) and strength (70 MPa).[1] To improve these properties, various elements are added to aluminum to modify the phase structure during either the crystallization step or heat treatment. The two types of aluminum alloys include casting alloys, which mainly contain silicon, and wrought alloys. The latter group can be further subdivided into manganese and magnesium alloys, which are strengthened by work hardening, and copper and zinc alloys, which are strengthened by precipitation hardening. The properties of aluminum can be significantly enhanced by
SYLWIA CIOŁEK, STANISŁAW JO´Z´WIAK, and KRZYSZTOF KARCZEWSKI are with the Department of Advanced Materials and Technologies, Faculty of Advanced Technologies and Chemistry, Military University of Technology, 2 Gen. S. Urbanowicza St., 00-908 Warsaw, Poland. Contact e-mail: [email protected] Manuscript submitted June 19, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS A
strengthening mechanisms, and the fabrication of alloys which, together with its low density, has resulted in its wide use in various industries. Despite the existence of a wide range of well-known aluminum alloys since the 1930s, numerous studies of reinforcement growth and the effects of various factors, such as the size and distribution of the precipitates, on the resulting mechanical properties have been and are still being performed. The study in this field is twofold. On one hand, research efforts are focused on modifying the production processes of well-known alloys by introducing new technologies, such as powder metallurgy, which was used to produce Al-Cu alloys,[2] or by tuning the chemical composition to produce reinforcing phases in the aluminum matrix. For example, Varin[3] prepared Al-Zr particles in an aluminum matrix to increase the hardness of the material. On the other hand, cheaper materials that are easier to use in the synthesis, such as iron, which is commonly used in construction materials, can be employed as reinforcing components. In his study, Srivastava showed that an Fe content ranging from 1.67 to 11.2 pct in aluminum-iron alloys significantly improves the alloy strength and tribological properties, due to the precipitation of the low-symmetry, high-aluminum phase FeAl3.[4,5] The undeniable potential of these particles to reinforce aluminum alloys is due to the complexity of the crystal structure, which gives rise to high hardness and abrasion resistance.[6] In addition, these particles are cheaper than intermetallic phases containing other elements that are use
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