The effect of microstructure on hardness measurements in the aluminium-rich corner of the Al-Ni-Cr system

Arc-melted Al-rich samples from the Al-Cr-Ni system were analysed using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. All of the expected binary phases were observed and identified. The binary phase with the largest extension into the ternary was Al3Ni2 at about 12 at.%. Three separate ternary phases were identified from the microstructures, and were found to agree reasonably with the compositions in the literature, although the phase fields had different shapes. Vicker's microhardness measurements have indicated that the phase hardnesses in decreasing order are most likely: Al3Ni2, phi, (alpha Cr), rho, Al4Cr, Al7Cr, Al11Cr2, Al9Cr4, Al3Ni and (Al). The phi, Al4Cr, Al11Cr2 and Al3Ni phases were brittle in massive form. (C) 2001 Elsevier Science B.V. All rights reserved.