The Structure And Properties Of Quinary High Entropy Alloys With High Melting Temperature

High entropy alloys with multi-principal elements is a novel concept for alloy design, which breaks through the traditional alloy design frame work on the base of"one or two major alloy elements", and became one of hot research topics in materials science and engineering. High entropy alloys are composed of five or more elements which have equal mole or near equal mole ratios. High entropy effects in high entropy alloys arising from the mixture of multi-principal elements, promote the random solid solution with simple BCC or FCC structures and usually with a little intermetallics within the grains. These simple structures usually have relatively good mechanical properties and corrosion resistance due to the solid solution and dissemination strengthening effects. As a result, high entropy alloys have great potential applications.In this work, high entropy alloys with equal mole ratios of five elements which selected from Ti,Zr,Hf,V,Nb,Ta and Mo were prepared by NCAM. The microstructures, phase structures and phase transformation points were systematacially investigated by OM, SEM, EDS, XRD and DTA. Furthermore, the macrohardness, microhardness, compression properties, abrasion resistance and corrosion resistance were also studied.It was found that the phases of all the high entropy alloys in this study are simple BCC or HCP or BCC+HCP solid solution structure, and form dendritic structures during solidification. Laves phase was observed in ZrVMoHfTi and ZrVMoHfNb alloy. The hardness of the six high entropy alloys is in the range from 334HB to 522HB, and the compressive strength is in the range from 1663MPa to 2060MPa.There is no plastic deformation before fracture in the alloys of ZrVMoHfTi and ZrVMoHfNb both of which contain Laves phase. The fracture behavior belongs to cleavage fracture. However, some plastic deformations before fracture in the other alloys were observed. The ZrVMoHfNb alloy performs the best abrasion resistance in the six high entropy alloys. The TiZrHfNbMo alloy performs the best corrosion resistance due to the formation of sole and uniform BBC solid solution. The polarization test is carried on the alloy in the 12N sulfur acid. In the test, the corrosion potential is greater than zero, and the breakdown of the passivating film do not occur until the potential rise up to 10V.