Preparation And Properties Of FeBSiZr Bulk Amorphous Alloys

Because of the special structure of long-range disordered and short-range ordered,amorphous alloys have some properties which are not possessed by other traditional metal materials.Among them,Fe-based bulk glassy alloys have advantages of high strength,excellent soft magnetic properties and low cost,and have received widespread attention in various fields,including soft magnetic materials and corrosion resistant materials.Since Zr with large atomic size and B with small atomic size are helpful to the formation ability of Fe-based amorphous alloys,this thesis developed FeBSiZr series bulk amorphous alloys with high saturation magnetic induction strength and corrosion resistance,and studied their thermodynamic properties,corrosion resistance,magnetic properties and mechanical properties.The main research contents are as follows:（1）Amorphous alloy strip Fe_71.9-xB_16.7Si_8.3Zr_3.1+x（x=0,0.1,0.2,0.3,0.4 at.%）and bar with critical size of 2 mm were prepared by changing the content of Zr,and the influence of Zr content on the thermodynamic properties of the alloy system was studied.It is found that with Zr content increasing from 3.1 at.%to 3.5 at.%,the interval of supercooled liquid phase increases from 47 K to 51 K.The atomic size differenceδ,mixing enthalpyΔH_mixand mixing entropyΔS_mixincrease gradually,indicating that the alloy system has high thermal stability and glass forming ability.（2）The corrosion resistance of Fe_71.9-xB_16.7Si_8.3Zr_3.1+x（x=0,0.1,0.2,0.3,0.4 at.%）amorphous alloy was tested by electrochemical workstation.In 1 mol/L H₂SO₄solution,the amorphous alloy sample with 3.3 at.%Zr has the best corrosion resistance.The self-corrosion potential and self-corrosion current density are 354 m V and 5.665×10^-7A/cm²,respectively.In 3.5%Na Cl solution,the amorphous alloy samples with 3.4at.%Zr have the best corrosion resistance,and the self-corrosion potential and self-corrosion current density are 147 m V and 4.951×10^-7A/cm²,respectively.（3）The magnetic properties of Fe_71.9-xB_16.7Si_8.3Zr_3.1+x（x=0,0.1,0.2,0.3,0.4 at.%）amorphous alloy were tested by VSM and B-H tester.It was found that although the saturation magnetic induction intensity of the alloy system decreased slightly,the coercivity Hc also decreased after the addition of elements.When Zr content is 3.1at.%,B_sis the highest（1.42 T）.The lowest coercive H_cis 9.53 A/m when Zr content is 3.5at.%.（4）The mechanical properties of the amorphous alloy were tested,and it was found that with the increase of Zr content,the Vickers hardness and compressive fracture strength gradually increased to 1133 Hv and 3591 MPa,respectively.Through SEM observation of fracture morphology,it is found that the section has a relatively obvious shell shape,but no vein pattern is observed.In addition,the smooth area also shows a tearing fracture mode,which is a typical brittle fracture feature.