Research On Structure Relaxation, Crystallization And Magnetic Property Of Fe-based Amorphous

The flakes and ribbons of Fe-(Al,Ga)-(P,B,Si,C) amorphous alloys were prepared by copper mold casting and melt-spinning.The structure relaxation,crystallization and magnetic property of Fe-(Al,Ga)-(P,B,Si,C) amorphous alloys were investigated by XRD,DSC,TEM and VSM.Fe₆₈Ni₁Al₅Ga₂P_9.65B_4.6Si₃C_6.75 amorphous alloys was amorphous structure and no crystals appeared in amorphous by pre-annealing at 573K,673K for 1h.The annealing process of structure relaxation happened in amorphous alloys in the following glass transition temperature T_g.Free energy of the whole system decreased after structure relaxation.Amorphous alloys were at a lower energy state after high temperature structure relaxation.Pre-annealing time and pre-annealing temperature had prominent effects on structure relaxation and crystallization process.Glass transition temperature T_g and specific heatΔC_p,g increase gradually with the augment of pre-annealing time and temperature.The crystallization temperature fallen as a result of the delay of pre-annealed time.The effects of cryogenic and cold-hot circle treatment on amorphous alloys had a similar function with pre-annealing.Strong effects of cold-hot circle treatment made structure relaxation had a entirety reaction.Large numbers of clusters appeared on amorphous matrix,and then there were nano-crystalline appearance.The saturation magnetization(Ms) enhanced and the coercive force(Hc) didn't change.The investigation of crystallization kinetics showed that glass transition and crystallization of Fe₆₈Ni₁Al₅Ga₂P_9.65B_4.6Si₃C_6.75 amorphous alloys had obvious crystallization kinetics effects. Amorphous alloys had excellent thermal stability.The activation energy for T_g,T_x,T_p1,T_p2were 703 kJ/mol,374kJ/mol,446 kJ/mol and 723kJ/mol respectively by using the method of Kissinger.The crystallization process wasα-Fe→α-Fe(Si)+Fe₃P(few)α-Fe+Fe₂P +Fe₃P +Ni₃P.The type of crystallization was primary crystal and eutectic.In the experiment of Fe₆₅Ni₄Al₅Ga₂P_9.65B_4.6Si₃C_6.75 amorphous alloys continuous isothermal annealing,α-Fe(Si) had already began to precipitation a little,when annealing temperature was below 450℃;large numbers of other crystal commenced,when annealing temperature was greater than 450℃.They were primarilyα-Fe(Si),Fe₂P,Fe₃P,Ni₃P,AlNi₃C_0.5 and other unknown crystal.The average size of crystalline for 450℃,500℃,550℃was 18.3nm,26.9nm,47.2nm respectively.It can be seen obviously that crystalline size increased gradually,when temperature was between 480℃and 600℃.Crystalline size got larger sharply at above 550℃.The volume fraction of simplex nano-crystallineα-Fe(Si) was 12%by calculating the area of exothermic peak.The saturation magnetization(Ms) of Fe₆₉Al₅Ga₂P_9.65B_4.6Si₃C_6.75 amorphous alloys climbed up and then declined with the rise in annealing temperature.It was 7900Oe at 450℃,while 4400Oe at 540℃.The coercive force(Hc) is smaller below 490℃,it increased abruptly at 510℃.The soft magnetic properties worsen rapidly.The remanence ratio is 0.049 at 450℃,while 0.044 at 490℃.To amorphous alloys,high Ms and excellent soft magnetic property exist a contradiction on unity.