Phase investigations of the AlIr system

The phase behavior of the AlIr system has been studied using differential thermal analysis, electron microprobe analysis, X-ray diffraction, chemical analysis and X-ray fluorescence. Our work confirms the existence of four compounds: Al 9Ir 2, Al 3Ir, Al 2.7Ir and AlIr. We also observed an additional intermetallic phase, with a stoichiometry corresponding to Al 13Ir 4; however, this compound exhibits a complex X-ray pattern and currently no structure has been determined. Peritectic temperatures were determined for Al 9Ir 2 (900 °C), Al 13Ir 4 (1015 °C) and Al 3Ir (1450 °C). The Al 2.7Ir phase is stable to above 1450 °C, and the congruent melting temperature of AlIr is 2120 ± 20 ° C. The solubility of aluminum in iridium was measured between 1085 and 1850 °C, and the maximum solid solubility was extrapolated to 18 at.% at 2058 °C. The maximum solid solubility of iridium in aluminum was measured to be less than 0.1 at.%. A phase diagram for the AlIr system is presented.