Microstructure and Mechanical Properties of Ti–Al–Ni–Cr–Co–Fe-Based High-Entropy Alloys

Four alloys with nominal compositions of TiAlNiCr, TiAlNiCrCo, TiAlNiCrFe and TiAlNiCrCoFe were synthesized through mechanical alloying followed by spark plasma sintering (SPS). After 8 h of milling, all the alloys developed a major parental BCC phase. SPS done on the alloys revealed that the BCC phase was retained after SPS. Sintering promoted the formation of one more BCC phase thus making the final microstructure comprised of two BCC phases. The phases were characterized using X-ray diffraction and scanning electron microscope. Backscattered electron images of the samples indicated that one BCC phase was rich in Ni and Al, whereas the second BCC phase was rich in Cr, Co and Fe. All the alloys showed good hardness and mechanical strength with values above 2000 MPa except TiAlNiCr.