Study Of Melt Hydrogenation On Microstructures And Properties Of Refractory TiZrNbHf_0.5Mo_0.5 High-entropy Alloy

Based on the concept of high-entropy alloys,the refractory high-entropy alloys based on refractory elements have become a hot spot in the aspect of high-temperature structural materials with its unique structures and properties.However,refractory high-entropy alloys has relatively low room-temperature ductility and high density which limited its application prospects.In order to solve the problem of low room temperature ductility of refractory high-entropy alloys and develop new high-plasticity and high-strenhgth refractory high entropy alloys,the hydrogen-containing TiZrNbHf_0.5Mo_0.5 refractory high entropy alloys were prepared by arc melting with melt hydrogenation technology.Hot working forging and Al alloying of the hydrogen-containing alloy were carried out to realize the ductilizastion of TiZrNbHf_0.5Mo_0.5 refractory high-entropy alloy.The hydrogenated and unhydrogenated TiZrNbHf_0.5Mo_0.5 refractory high-entropy alloys are composed of a single disordered BCC phase.Hydrogenation does not change the crystal structure of the refractory high-entropy alloy.A certain amount of hydrogen can refine the dendrite structure and decrease the average size of the grains.Hydrogenation can significantly improve the plastic and compressive strength of TiZrNbHf_0.5Mo_0.5 refractory high-entropy alloys.In addition,melt hydrogenation can effectively increase the strength of TiZrNbHf_0.5Mo_0.5 refractory high entropy alloys at elevated temperature,while does not change the compressive ductility.The room temperature compressive strengths of hydrogenated and unhydrogenated alloys were1755 MPa and 1322 MPa,respectively,and the fracture strains were 22.5%and 38.9%,respectively.Hot working forging is performed on the hydrogenated alloy.Forging does not change the crystal structure of the refractory high-entropy alloy.After hot working forging,the grains are broken and aligned perpendicular to the forging direction,and the alloy structure is refined.Hydrogen can significantly reduce the density and pile up of dislocations in the forged alloy and further refine the grains.Forging can improve the mechanical properties of the alloy.After the process of melt hydrogenation and hot working forging,the strength and plasticity of the alloy will be greatly improved.A certain amount of hydrogen will cause the forged alloy have a room temperature compressive strength of more than 3100MPa,a fracture strain of more than 55%.Moreover,its compressive strength at 900?will reach 948MPa,while the strength of the as-cast alloy is 636 MPa.The effect of melt hydrogenation on Al-alloyed TiZrNbHf_0.5Mo_0.5 refractory high-entropy alloy was investigated.A certain amount of Al and H element can slightly refine the grains,which can increase the strength of the alloy while improving the plasticity of the alloy.The addition of Al can slightly increase the yield strength of the refractory high-entropy alloy by solution strengthening.The compressive strength of the TiZrNbHf_0.5Mo_0.5Al_0.1 alloy smelted under 10%hydrogen exceeded 2000MPa,and the fracture strain reached 60%.Through the processes of melt hydrogenation,hot working forging or Al alloying,we have achieved the strengthening and toughening of TiZrNbHf_0.5Mo_0.5 refractory high-entropy alloys.