On the constitution of the high-Al region of the Al–Cr alloy system

Complex orthorhombic phase in the Al–Cr–Fe system

“…It has revealed a complex structure different from both the hexagonal μ-Al 4 Cr binary phase (P6 3 /mmc, a ≈ 2.00 nm and c ≈ 2.47 nm), which is isostructural to the μ-Al 4 Mn phase [4][5][6], and orthorhombic ε-Al 4 Cr (orthorhombic base-centered lattice, a ≈3.46 nm, b ≈ 2.00 nm, and c ≈ 1.26 nm) and ε′-Al 4 Cr phases (orthorhombic primitive lattice, a ≈ 3.46 nm, b ≈ 2.00 nm, and c ≈ 1.26 nm) [4]. As shown in [7], these structures correspond to none of the equilibrium phases in the Al-Cr binary system, but the ε-Al 4 Cr phase has been revealed in the Al-CrNi ternary system in alloys close to the Al 4 Cr stoichiometry with low Ni content. According to electron diffraction ( Fig.…”

“…No ternary compounds have been revealed in this study. The x-ray diffraction pattern of alloy having the composition Al 75 Cr 19.9 Fe 5.1 [2] that falls within the μ-solid solution region is interpreted as that belonging to the hexagonal solid solution based on the μ-phase (Al 4 Cr) described in [3][4][5][6][7]. We have analyzed these data and found the above conclusion to be mistaken.…”

Peritectic reaction on the Al-rich side of Al–Cr system

“…The binary Al-Cr system has been studied by many authors because of the existence of several structurally complex phases on the Al-rich side of the phase diagram [1][2][3][4]. For example, Al 45-Cr 7 (or Al 13 Cr 2 , or Al 7 Cr), Al 11 Cr 2 (or Al 5 Cr) and Al 4 Cr are some of the known complex phases that exist in this region.…”

“…On the nature of the invariant reaction between the liquid, the fcc-Al phase and Al 45 Cr 7 , there is a long-lasting controversy: the fcc-Al phase was considered to form with a peritectic reaction by Fink and Freche (1933) [8], Bradley et al (1937) [9], Harding and Raynor (1952) [5], Zoller (1960) [10] and Murray (1998) [4], while Goto and Dogane (1927) [11], Neto et al (1992) [12], Mahdouk and Gachon (2000) [3], Du et al (2005) [13], Okamoto (2008) [14], Grushko et al (2008) [2] and Almeida and Vilar (2010) [15] proposed a eutectic reaction.…”

The Al–Cr–Fe phase diagram. II. Liquidus surface and phase equilibria for crystallization of 58–100 at.% Al alloys

“…Concerning the respective field (p 11 U 7 U 8 e 6 ) for the θ phase, it hardly reaches 1 at.% Fe, decreasing toward the aluminum corner in the ternary system. This has been established through a comparison of the liquidus temperatures of ternary alloys, based on which the temperatures of four-phase invariant equilibria have been established and correspond to the invariant points U 4 (1035°C), U 5 (985°C), and U 7 (750°C) ( Table 1), and the liquidus curves and temperatures of invariant equilibria in the binary Al-Cr system, according to our version of the phase diagram [7][8][9]. μ phases at 980 and 985°C, takes part in the invariant reaction L + μ ⇔ η, whose temperature is 865°C, in the ternary system.…”