Preparation And Antioxidation Performance Of Ta-W Based Self-oxidation Alloys And High-entropy Alloys

Ta-W based anti-oxidation alloy and equal mole ratio Mo25Nb25 Ta25W25 high entropy alloy(HE A)were prepared by hot-press sintering.The oxidation behaviors of alloys were analyzed.There are two parts in this work:Ta-W based alloys were prepared by hot-pressing sintering,the phase composition and hardenss of alloy were analyzed,the oxidation behaviors of alloys at 800??900? and 1000 ? were studied,then oxidation kinetics were explored by ananlyzing the phase compositions on microstructure of oxide layer at different tempers ture.The effect of addition of Al element on phase composition?oxidation kinetics and oxidation products of alloy were investegaed.The results showed:(1)Ta-10W alloy was prepared by hot-pressing sintering,W dissolved in Ta and formed solid solution.The relative density of alloy is 95.88%.The oxidation weight gain curve of Ta-10W alloy after oxidation at 800??900? and 1000? followed the linear law.Oxidation product was Ta22W4067.The Vickers hardness of alloy was 5.43GPa.(2)The nano-sized Ta0.9Al0.1 solid solution was prepared by mechanical alloying at a rotation speed of 300 r/min,48 hours milling time,with 10:1 ball ratio and solid-liquid ratio.Agglomeration occurred after 48 hours of ball milling.TG analysis showed that the precipitation of Al elemental when Ta0.9Al0.1 solid solution annealed at 600?.(3)Ta-10W-6Al alloy was prepared by hot-pressing sintering,The phase composition of Ta-10W-6Al alloy were consisted of AlTa2 intermetallic compound and Ta solid solution.The oxidation weight gain curve of Ta-10W-6Al alloy after oxidation at 800??900? and 1000?followed the parabolic law.The oxide layer were mainly composed of Ta22W4067 and Al2O3 after oxidation at 800?,the oxide layer is mainly composed of Ta22W4067 ?Al2O3 after oxidation at 1000?.The Vickers hardness of alloy was 7.45GPa.Equal mole ratio Mo25Nb25Ta25W25 high entropy alloy(HE A)prepared by hot-pressing sintering,the effect of holding time on the phase and homogeneity of the alloy was study.The oxidation kinetics of alloy at 800??900? and 1000? were explored,phase compositions at different tempers ture and mechanical properties of alloy were analyzed.The effect of addition of 1 wt%TiB2 and ZrB2 on phase composition?oxidation kinetics?oxidation products and mechanical property of alloy.The results showed:(1)Equal mole ratio Mo25Nb25Ta25W25 alloy(HE A)prepared by hot-pressing sintering,the alloy had simple BCC structure and the relative density was 96.09%.Extending the holding time was benefit to the diffusion of elements in the alloy.The oxidation weight gain curve of Mo25Nb25Ta25W25 after oxidation at 800? followed the parabolic law.As the oxidation temperature increased,the parabolic law turned to the liner law.Oxidation products were Ta16W18O94 and Nb14W3O44.During the oxidation process,the oxide film became loosen and spalled from the matrix due to volatilization of Mo03.The Vickers hardness of alloy was 4.44GPa.Adding lwt%TiB2 and ZrB2 were addied into high-entropy alloy,the alloys have simple BCC structure after hot-pressing sintering.The relative densities were 95.84%and 96.23%,respectively.The oxidation weight gain curve of Mo25Nb25Ta25W25 alloy after oxidation at 800??900? and 1000? followed the parabolic law.During the oxidation process,protective Ti02 and liquid phase B2O3 were generated,however,as the oxidation temperature and the oxidation time increased,the oxide film became loosen and spalled from the matrix due to volatilization of MoO3 and the liquid phase of B2O3.The Vickers hardnesses of alloys were 5.01 GPa and 4.70GPa.