Precipitation of Cr-rich phases in a Ni-50Al-2Cr (at.%) alloy

An as-cast Al-rich B2-ordered Ni-50Al-2Cr alloy was heat-treated at 550 °C for 500 h and then analysed by using atom probe field-ion microscopy (APFIM), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Chromium-rich precipitates with (unexpectedly) high Al contents were detected and identified as the so-called 'X-phase'. The α-chromium phase was also present possessing a significantly lower Al content. Nanoscale B2-ordered NiAl precipitates present in the X-phase as well as nanoscale X-phase precipitates within B2-ordered NiAl were detected.