Preparation And Study On Microstructure And Properties Of Refractory High Entropy Alloys

As a kind of new alloy material,high entropy alloys break through the traditional alloy design concept on the base of “one or two major alloy elements”.High entropy alloys are composed of five or more elements which have equal mole or near equal mole ratios and prepared by vacuum non-consumable arc-melting or mechnical alloying and so on.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,which can strengthen the properties.By optimizing the design of alloy composition we can obtain high strength,high hardness,corrosion resistance and abrasion resistance. As a result,high entropy alloys have great potential applications.In this work,WNbMoTaV、ZrTiMoTaV and ZrTiHfTaV with equal mole ratios of five elements which selected from W、Nb、Mo、Ta、V、Zr、Hf and Ti were prepared by NCAM.The microstructres,phase structures were studied by XRD、OM、SEM、EDS and TEM.Furthermore the microhardness,static,dynamic and high-temperature compressive strength were studied.High-temperature annealing experiments on WNbMoTaV alloy were conducted at 1350℃,1550℃,1750℃ and 1950℃.Then investigate the microstructure and properties after annealing.It was found that the phase structures of WNbMoTaV and ZrTiHfTaV were single BCC.ZrTiMoTaV alloy were BCC and a phase which contained V.The microstructures of these alloys were dendritic morphology.The microhardness of WNbMoTaV alloy is 575 HV,ZrTiMoTaV alloy is 511 HV and ZrTiHfTaV alloy is 411.4HV.The static compressive strength of these three alloys are all among 1919-2284 MPa.The dynamic compression curves suggest that they have not strain rate strengthing effects.The high-temperature compression curves indicate that WNbMoTaV alloy is fit for high-temperature application.Neither ZrTiMoTaV nor ZrTiHfTaV is fit for high temperature application above 800℃ as a result their high-temperature strength are very low.After high-temperature annealing,phase structure of WNbMoTaV alloy remains unchanged,microstructure tends to homogenization.