Mechanical Behavior Of Fe₇₈Si₉B₁₃ Amorphous Alloy And Its Laminated Composites At High Temperature

Fe-based amorphous alloys have been widely used and researched due to the advantages of high strength,high hardness and good magnetic properties.However,Fe-based amorphous alloys will produce highly localized shear bands during the room temperature deformation process.Once the shear bands are initiated,they will rapidly expand,which leads to its macroscopic appearance as elastic brittle fracture.After research,it has been found that Fe-based amorphous alloys and Al-based amorphous alloys with primary crystalline exhibit obvious strain hardening during high-temperature tensile.The dense oxide film formed on the surface of the Al-based amorphous alloy can prevent its high-temperature oxidation,but Fe-based amorphous alloys are easily oxidized during high-temperature tensile.Then whether the high-temperature oxidation of the Fe-based amorphous alloy will affect the strain hardening,it is necessary to further study the effect of oxidation on strain hardening.In this paper,the Fe₇₈Si₉B₁₃amorphous alloy with the primary crystalline is selected,and the laminated Ni/Fe₇₈Si₉B₁₃/Ni composite material is prepared by electrodeposition.The effects of temperature,holding time,initial strain rate,and Ni layer thickness on the high-temperature deformation behavior of the Fe₇₈Si₉B₁₃amorphous alloy and the laminated Ni/Fe₇₈Si₉B₁₃/Ni composites were studied by tensile tests under different conditions.The structure characterization and microscopic morphology observation of the material are carried out to explore its fracture behavior.The high temperature tensile tests of the Fe₇₈Si₉B₁₃amorphous alloy and the laminated Ni/Fe₇₈Si₉B₁₃/Ni composite material show that both of them have a single shear band and brittle fracture at room temperature,the tensile strength can reach 2303 MPa and 1779 MPa,respectively,with high strength.As the temperature increases,their plasticity gradually increases.Strain hardening occurs at 510℃,and the fracture strain can reach 0.340 and 0.424 respectively,showing good plastic denaturation ability.Due to the protective effect of the electrodeposited Ni layer,the laminated Ni/Fe₇₈Si₉B₁₃/Ni composite material has stronger plasticity than the original Fe₇₈Si₉B₁₃amorphous alloy.Holding at high temperature for different time will affect the strain hardening phenomenon and mechanical properties of the Fe₇₈Si₉B₁₃amorphous alloy.When the holding time is before the end of the initial crystallization peak,the amorphous alloy will undergo strain hardening,which further explains that dynamic crystallization induces strain hardening.The Fe₇₈Si₉B₁₃amorphous alloy and the laminated Ni/Fe₇₈Si₉B₁₃/Ni composite material are sensitive to the initial strain rate during high temperature tensile.When the initial strain rate is3.33×10^-4s^-1at 490℃ and when the initial strain rate is 3.33×10^-4s^-1and 1.67×10^-4s^-1at 510℃,strain hardening will occur.It can significantly improve the plasticity.When the Ni layer thickness is 11μm and the initial strain rate is 3.33×10^-4s^-1at 510℃,the fracture strain of the laminated composite reaches the maximum value of 0.424,and the plastic deformation ability is the strongest.