Modulation Of Nanocrystallization Precipitation And Properties Of FeCoNi-based Amorphous Alloys

Amorphous alloys have been attracting close attention because of their excellent soft magnetic properties.As the core component of power transformers,inductors,mutual inductors and filters,magnetic cores have been subjected to higher requirements for their soft magnetic properties in recent years.Fe Co Ni-based amorphous alloys have excellent soft magnetic properties.The partial replacement of Fe atoms by Co atoms reduces the magnetostriction coefficient of the amorphous phase and lowers the coercivity of the material,and the high content of Ni atoms helps to reduce the magnetic permeability of the material.The study of the soft magnetic properties of Fe Co Ni-based amorphous alloys has important theoretical guidance and practical application value for further in-depth research.In this thesis,the Fe-Si-B alloy system is used as the basis,and the Si and B atoms are determined to be 6 at.% and 14 at.%,respectively.The alloy composition was designed by replacing the Fe atoms in the Fe80Si6B14 alloy with the addition of Co and Ni atomic ratio of1:1.The alloy strips were prepared by a single-roller strip dumping process.Structural characterization of the quenched alloy strips and the heat-treated alloy strips was carried out by X-ray diffractometry（XRD）.The thermal stability of the quenched alloy strips was analyzed by differential scanning calorimetry（DSC）to provide a reference for the heat treatment process parameters.The DC and AC soft magnetic properties of the cores of the alloy strips were studied by DC soft magnetic measurement device and AC soft magnetic measurement device,respectively.The inductance of the alloy strip cores was studied by a3260 B precision magnetic component analyzer,and the effective permeability of the strip cores was calculated using the effective permeability formula.The main results are as follows:（1）For the five-component Fe80-2x Cox Nix Si6B14（x=0,5,10,15,20 and 25）quenched alloy strips,the amorphous formation ability of the alloy is poor when the atomic content of Co and Ni（x=0,5 and 10）is low.When the atomic content of Co and Ni（x=15,20 and 25）is higher,the amorphous formation ability of the quenched alloy strips is stronger.（2）The first onset crystallization temperatures of Fe50Co15Ni15Si6B14 、Fe40Co20Ni20Si6B14 和 Fe30Co25Ni25Si6B14 strips were 498 °C,510 °C and 503°C,respectively.When the heat treatment temperature is lower than the first onset crystallization temperature,the presence of micro-nanocrystals or clusters inside the strip reduces the activation energy of the initial crystalline phase,prompting the precipitation of α-Fe crystalline phase in the alloy strip and its rapid growth.（3）The Fe50Co15Ni15Si6B14、Fe40Co20Ni20Si6B14 和 Fe30Co25Ni25Si6B14 alloy strip cores exhibited good DC soft magnetic properties after being held at 440 °C for 10 min.The saturation magnetic induction strengths were 0.91 T,0.83 T and 0.89 T,and the coercivity were 23.7 A/m,15.3 A/m and 13.0 A/m,respectively.（4）The alloy strip cores of Fe50Co15Ni15Si6B14 and Fe40Co20Ni20Si6B14 have low coercivity and loss after holding at 480 °C for 10 min,and both coercivity and loss decrease significantly with increasing frequency.At 10 k Hz,the coercivity was 15.0 A/m and 16.4A/m,and the losses were 10.65 W/kg and 7.8 W/kg,respectively.The alloy strip cores of Fe30Co25Ni25Si6B14 alloy strip cores after being held at 440 °C for 10 min showed good AC soft magnetic properties,with coercivity and loss of 16.4 A/m and 6.55 W/kg at 10 k Hz,respectively.（5）For Fe62-x Cox Ni18Si6B14（x = 2 and 4）alloy,which is not easy to prepare amorphous alloy strips,the amorphous formation ability of the alloy was significantly improved by adding 4at.% V atoms instead of Fe atoms.The prepared Fe56Co2Ni18Si6B14V4 alloy strip cores,which were subjected to 420 °C and held for 10 min,exhibited good soft magnetic properties.It has high saturation magnetic induction strength（0.86 T）and low coercivity（4.4 A/m）.Also,its AC soft magnetic properties are relatively good,with a coercivity of 5.7A/m,loss of 2.68 W/kg,and effective permeability of 4.49 k at 10 k Hz.