Microstructure and mechanical properties of TiZrTaxNbMo refractory high-entropy alloys

DONG Fuyu; GUO Zihe; ZHANG Yue; SHEN Xiangyang; YUAN Xiaoguang

doi:10.7688/j.issn.1000-1646.2025.04.16

Abstract：[Objective]As a new kind of high-temperature materials,refractory high-entropy alloys have a wide application prospect because of their excellent high-temperature performance.However,their poor plasticity at room temperature has become the main factor limiting their development.Among many refractory high-entropy alloy components,TiZrTaNbMo has good biocompatibility and has attracted extensive research interest.Similarly,the alloy also has the disadvantage of poor plasticity at room temperature,which limits the development of the alloy.Ta element is the element with the highest melting point in the component.So far,the mechanisms underlying the influences of Ta element on the microstructure and mechanical properties of the alloy system have remained unclear.[Methods]The influences of the decrease in Ta content on the microstructure and properties of TiZrTaNbMo refractory high-entropy alloy were studied.In this study,the x value in TiZrTaxNbMo which reflected Ta molar ratio was 0.8,0.9,and 1.0,and the molar ratio of other elements remained unchanged.TiZrTarNbMo(x=0.8,0.9,1.0)series refractory high-entropy alloys were prepared by non-consumable high-vacuum arc furnace melting,and the alloy matrix was annealed at 1 000℃/6 h,which was followed by natural cooling with the furnace.The phase structures of the alloys were determined by an X-ray diffractometer(XRD).The microstructures and element distributions of the alloys were characterized by a scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).The Vickers hardness of the alloys was measured by a microhardness tester.[Results]The TiZrTaxNbMo refractory high-entropy alloys are composed of the primary BCC1 phase and the secondary BCC2 phase,showing a typical dendritic structure.With the increase in Ta content,the interdendritic region becomes smaller.Ta,Nb,and Mo elements are enriched in the branches,while Ti and Zr elements are enriched in the interdendritic region.The decrease in Ta content reduces the segregation of Nb and Mo elements in the branches.In terms of mechanical properties,increasing Ta content increases the hardness of the alloys from 433 HV to 501 HV.The experimental results indicate that the change in Ta content does not cause the change in the crystal structures of the alloys,and they still have a BCC biphase structure.The decrease in Ta content leads to the enlargement of interdendritic region of metal dendritic structure.Reducing Ta content is helpful to reduce the segregation of elements,especially for Ti and Zr elements with lower melting points.[Conclusion]In this study,the original design of refractory high-entropy alloys with an equal molar ratio is changed,and the composition is optimized.The micro structure and mechanical properties of the alloys are improved by the adjustment of element content.The research results will help to promote the further application of the TiZrTaNbMo refractory high-entropy alloy system.