Investigation of multi-phase strengthened Ni36Co30Cr11Fe11Al8Ta4 high entropy alloy prepared by directional solidification

Abstract

The directional solidification Ni36Co30Cr11Fe11Al8Ta4 high entropy alloys were prepared by changing the withdraw rates to reveal the phase formation and reinforcing mechanism. The different withdraw rates changes microstructure of the alloy. The primary dendrite spacing was reduced from 250 μm to 100 μm. L12 phases were observed in inter-dendritic region. The phase analysis result indicates that the Laves phases are nucleated first. When the withdraw rate increases from 5 μm s−1 to 100 μm s−1, the yield strength increases from 556.21 MPa to 664.31 MPa. The directional solidification alloy shows the higher strain than the as-cast alloy. The dislocation loops can be observed due to the high misfit of L12 phases. The main strength mechanisms are Orowan bypassing mechanism and interface strengthening mechanism.