Local mechanical properties of AlxCoCrCuFeNi high entropy alloy characterized using nanoindentation

With the addition of Al element, the microstructure of high entropy alloy AlxCoCrCuFeNi (x = 0.5, 1.5 and 3.0) changes from single FCC to FCC + BCC and then to single BCC phase. Hardness and elastic modulus of different phases in the HEAs are measured utilizing nanoindentation method. It is found that with the increase of the Al element, the hardness rises more significantly in the BCC phase than that in the FCC phase. The reason is attributed to that the Al element has a stronger solid-solution strengthening effect in the BCC phase, due to the larger elastic modulus mismatch. The precise characterization of local mechanical properties of different phases in the HEAs provides us opportunity to design alloys with desired performance.