Constitution of the high-Al region of Al-Cu-Rh

Phase equilibria between 540 and 1010 degrees C were studied in Al-Cu-Rh alloys containing more than 50 at.% Al. Congruent equiatomic AlRh dissolves more than 40 at.% Cu and extends up to 58 at.% Al at the high-Cu part of its compositional range. High-temperature cubic C-Al(5)Rh(2) (C-phase) dissolves up to 13 at.% Cu, "Al3Rh" (epsilon(6)-phase) up to 15 at.% Cu and Al(9)Rh(2) up to 1.5 at.% Cu. The solubility of the third element in other binary Al-Rh and Al-Cu phases is below 0.5 at.%. Close to the high-Cu limit of the C-phase region the fee C(2)-phase structurally related to the C-phase is formed. Stable decagonal phase (D1-phase) is formed below 1005 degrees C in a compositional range extending from Al(65)Cu(16)Rh(19) to Al(62)Cu(23)Rh(15), which shifts to higher Cu concentrations with decreasing temperature. An additional ternary phase forming around the Al(70)Cu(20)Rh(10) composition below 660 degrees C was revealed. Partial 1010, 990, 900, 800, 700, 600 and 540 degrees C isothermal sections were determined. (c) 2007 Elsevier B.V. All rights reserved.