Study Of The Effect Of Slight Addition Of Co On The Properties Of FeSiBHf Bulk Amorphous Alloy

The internal atomic structure of amorphous alloys differs from that of conventional crystalline alloys and,in comparison,offers performance advantages over ordinary metals,with iron-based amorphous alloys offering better soft magnetic properties.Under the background of"double carbon",Fe based amorphous alloy,as a green and energy-saving structural material and functional device material,has played its unique advantages in electronic components,power equipment and other fields.In this thesis,bulk amorphous alloys and amorphous ribbons of Fe Si BHf Co system were prepared by vacuum arc casting method and single roll strip casting method,respectively.The influence of the addition of trace Co on the properties of amorphous alloys of(Fe_72.5Si_8.3B_16.7Hf_2.5)_100-xCo_x（x=0,0.5,1,1.5,2）system was detected and analyzed by using relevant experimental equipment,revealing the correlation between the properties and components of the alloys.In addition,the crystallization kinetics of Fe_72.5Si_8.3B_16.7Hf_2.5and(Fe_72.5Si_8.3B_16.7Hf_2.5)₉₉Co₁amorphous alloys are systematically studied in combination with the non isothermal crystallization kinetics,revealing the crystallization process and nucleation and growth mechanism of the alloys.The experimental results show that:（1）The addition of trace Co elements can improve the stability of the subcooled liquid and the glass forming ability.With the increase of Co content,the width of the subcooled liquid phase zoneΔT_xof the alloy increased from 39 K to 48 K,and the mixing entropyΔS_mixincreased from 5.933 k J·mol^-1·K^-1to 7.584 k J·mol^-1·K^-1.The subcooled liquid stability of the alloy was the best at 2%Co content.（2）Fe_72.5Si_8.3B_16.7Hf_2.5and(Fe_72.5Si_8.3B_16.7Hf_2.5)₉₉Co₁amorphous alloys are easier to nucleate than to grow in the whole crystallization process;The crystal growth rate of the first precipitated phase of the two alloys was much lower than that of the later precipitated phase;The addition of 1%of Co element could improve the thermal stability of the alloy.（3）With the increase of Co content,the saturation magnetic induction value of the alloy increases and then decreases,and the coercivity gradually decreases,when the Co content is 1.5%,it has the highest B_sof 1.48 T.When the Co content is 2%,it has the lowest H_cof 0.9 A/m.The corrosion resistance of the alloy in 1 mol/L H₂SO₄solution is getting worse and worse.When no elemental Co is added,the alloy has the best corrosion resistance.The corrosion resistance of the alloy in 3.5%Na Cl solution is increasingly good,and the best corrosion resistance is achieved when 2%Co is added.（4）The addition of Co has a positive effect on the mechanical properties of the alloy.The overall hardness of the alloy is above 1100 H_v,and the compressive fracture strength of the alloy increases from 2934 MPa without adding Co to more than 3000 MPa.When the Co content is 2%,the alloy has the highest hardness and room temperature compressive strength,which are 1197 H_vand 3438 MPa,respectively.In addition,catastrophic brittle fracture occurs directly after the specimen undergoes elastic deformation,without showing plasticity.