Experimental Description of the Al-Cu Binary Phase Diagram
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ATURE REVIEW
A. Introduction
RELIABLE phase diagrams are essential for focused material development. The Al-Cu system, being the key binary system for many Al-based, Cu-based, and dural alloys, has been investigated intensively over recent decades owing to its importance to industry. The focus of most studies have been the Al-rich and Cu-rich parts of the phase diagram, respectively, which are used for interpreting microstructures of alloys that have been used in industrial applications. Knowledge of phase equilibria across the whole concentration range of a binary phase diagram is crucial for the extrapolation of material properties and thermodynamic modeling of higher order systems. Although the most recent
ONDREJ ZOBAC is with the Department of Inorganic Chemistry functional materials, University of Vienna, Wa¨hringer Straße 42, 1090 Vienna, Austria and also with the Institute of Physics of Materials, The Czech Academy of Sciences, Zizkova 22, 616 00 Brno, Czech Republic. Contact e-mail: [email protected] ALES KROUPA and ADELA ZEMANOVA are with the Institute of Physics of Materials, The Czech Academy of Sciences. KLAUS W. RICHTER is with the Department of Inorganic Chemistry - functional materials, University of Vienna. Manuscript submitted January 11, 2019. Article published online May 21, 2019 METALLURGICAL AND MATERIALS TRANSACTIONS A
experimental phase diagram, that was published by Ponweiser et al.[1] describes the whole concentration range, there are still some uncertainties and inconsistencies in the currently accepted version. Therefore, further experimental studies to clarify these points appear to be justified. B. Literature Review The Al-Cu phase diagram is characterized by many intermetallic phases with complex mutual relationships occurring in all regions of the phase diagram. The phase diagram has been studied by several authors, and several very comprehensive overviews have been published.[2–5] In the following section, we briefly discuss the state of knowledge of the binary phase diagram. For a better illustration of key points, a comparison of the evaluated phase diagram published by Murray[2] and that of Ponweiser et al.[1] is shown in Figure 1. Figure 1(a) shows the whole concentration range of the phase diagram, whereas Figure 1(b) shows just the central region. The maximum solubility of Cu in Al is equal to 2.5 at. pct at the eutectic temperature of 550 C.[2] The h-phase (Al2Cu) was described for the first time by Owen and Preston[6] and also by Friauf.[7] The phase was characterized using XRD (single-crystal rotational method), and a tetragonal symmetry was found. The crystal structure of the h-phase was determined later by
VOLUME 50A, AUGUST 2019—3805
ε
γ
(a)
(b) Fig. 1—Al-Cu phase diagrams adapted from Ref. [2] (dotted lines) and Ref. [1] (solid lines) (a) whole concentration range and (b) the central part of the phase diagram. Note that the labeling of the phases is consistent with Table I.
Havinga[8] as having an I4/mcm space group. The melting behavior of the h-phase has
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