Study On Preparation Of Fe-Cr-Mn-N Amorphous By Mechanical Alloys, Annealing And Magnetic Properties

The amorphous alloy with a wide super-cooled liquid region is a new material, have excellent mechanical properties and unique features, and it is one of the hot issues of domestic and international research in the field of materials science and engineering. And Fe-based amorphous alloy not only has excellent mechanical properties, but also has excellent soft magnetic properties, and has broad application prospects.In this thesis, Fe60Cr15Mn10N15 multi-amorphous alloy is chosen as the experimental subject, its high nitrogen content makes the common melting preparation which required high temperature and high nitrogen partial pressure greatly be possible to achieve, the temperature and nitrogen partial pressure for mechanical alloying (MA) technology are lower, thus it is a better way to prepare the amorphous alloy composition. In this thesis, XRD, SEM, DSC, VSM were used to study the amorphous formation process, annealing transition and magnetic properties ofFe60Cr15Mn10N15.The results shows that:Fe60Cr15Mn10N15 amorphous alloy can be prepared by mechanical alloying (MA) after milling 40h, the glass transition temperature Tg of the finally amorphous alloy is 437℃, the crystallization temperature Tx is 519℃, and the super-cooled liquid region ΔTx is 82℃; extending the milling time, amorphous alloy begins to precipitate crystalline phase Cr2N; in the whole process of MA, the organizational changes of the powder was:the mixed powder â†'supersaturated solid solution+Cr2Nâ†'amorphous alloyâ†' amorphous alloy+Cr2N; calculated by thermodynamic shows that the mixing chemical enthalpy ΔHchem of this system is-0.24KJ/mol, the amorphous formation enthalpy ΔHformis-6.610KJ/mol, thus the alloy system has a thermodynamic conditions for the formation of amorphous alloys; the 8%Mo element was used to replace Cr element, after milling 120h, the Mo peak was still existence; the 7%B element was used to replace N elements, after milling 120h, the Cr2N peak was still existence; the differential thermal analysis was used to analysis Fe60Cr15Mn10N15 amorphous alloy powder, as the increasing heating rate, the characteristic temperature of Fe60Cr15Mn10N15 amorphous alloys are moving to the direction of higher temperature, indicating it has a significant dynamic effects; by Kissinger equation fitting, the apparent activation energy were respectively:Eg= 117.75kJ/mol, Ex1=129.56 kJ/mol, by Losocka equation fitting, the Kauzmann temperature Tk=127K; the Fe60Cr15Mn10N15 amorphous alloy was isothermal annealing at different temperatures, the microstructure evolution in crystallization process of Fe60Cr15Mn10N15 amorphous alloy process was: amorphousâ†' amorphous alloy+Cr2N â†'α-Fe+Cr2N â†'α-Fe+CrN+Cr2N; the hysteresis loops of Fe60Cr15Mn10Ni5 amorphous alloy during the milling process and at different annealing temperature indicating that the alloy system with excellent soft magnetic properties; comprehensive comparison of the soft magnetic properties during the milling process and at different annealing temperatures, the alloy system has the optimal soft magnetic properties at the state of amorphous.