Investigation Of ZrB₂ On The Mechanical Property And Oxidation Resistance Property Of Mo-12Si-8.5B Alloys

Mo-Si-B alloys are one of attractive candidate materials for potential applications to replace Ni-base superalloys.In order to solve the conflict between the fracture toughness and high temperature oxidation resistance properties of Mo-Si-B alloys,doping in the Mo-Si-B alloys has been widely investigated to balance the mechanical and oxidation properties of the Mo-Si-B alloys.While ZrB2 is considered to be doped in Mo-Si-B alloys in this study.Mo-12Si-8.5B(at.%)alloys doped with different mass fraction of ZrB2 were processed by Mechanical alloying(MA)followed by hot pressing(HP).The influencing laws between the microstructure refinement,deformation behavior,and the oxidation behavior of Mo-12Si-8.5B alloys doped with different mass fraction ZrB2 were clarified,additionally the effect of ZrB2 on the oxidation resistance behavior and mechanism of Mo-12Si-8.5B alloys was investigated.The alloys are comprised with the Mo solid solution and the intermetallic phases Mo3Si and Mo5SiB2,along with the uniform dispersion of ZrO2,ZrB12 and other fine-sized particles,which contribute to further fine grain microstructures of ZrB2-doped Mo-12Si-8.5B alloys than the undoped one.Mechanical property tests were conducted at ambient temperature,and the compression strength of the ZrB2-doped Mo-12Si-8.5B alloys is improved with the increasing mass fraction of ZrB2.The addition of ZrB2 in the Mo-12Si-8.5B alloys improves the fracture toughness of alloys,and the fracture mode is transgranular and intergranular mixed fracture.There is no progress in impovement of flexure strength of Mo-122Si-8.5B alloys with the addition of ZrB2.The oxidation at 1300? showed that both the ZrB2-oped Mo-12Si-8.5B alloys and undoped Mo-12Si-8.5B alloy are covered with B-SiO2 scale,the new structure of scale for ZrB2-doped Mo-12Si-8.5B alloys is more protective.The ZrB2-doped Mo-12Si-8.5B alloys showed a superior oxidation resistance behavior compared to the undoped Mo-12Si-8.5B at 1 300?.It was abserved that the addition of ZrB2 has significant influence on the oxidation behavior of Mo-12Si-8.5B alloys:(i)the protective and stable silica scale was formed at a faster pace.(ii)the pores in the scale was especially sealed faster.(iii)the addition of ZrB2 promoted the rapid formation of a dense scale.