Study Of Positron Annihilation Lifetime In Structural And Structural Defects Of HITPERM Nano-alloy

HITPERM-type soft magnetic alloys Fe(Co)-M-B-Cu(M=Nb, Zr, Hf) exhibit excellent soft magnetic properties. It is currently one of the focal points in development of soft magnetic materials. In this paper, we used a lot of testing tools, such as X-ray diffraction (XRD), Mossbauer spectroscopy (MS), Positron annihilation spectroscopy (PAS), Transmission electron microscopy (TEM) and Differential thermal analysis (DTA) to researching mainly microstructure, structural defects and magnetic properties of (Fe1-xCox)86Hf7B6Cu1amorphous quenched alloys before and after middle-frequency magnetic pulsing treatment. Main tasks are summarized as follows:Constituents of (Fe1-xCox)86Hf7B6Cu1alloys were designed firstly. Then, master alloy was obtained by vacuum are furnace smelting equipment.,(Fe1-xCox)86Hf7B6Cu1(x=0.3～0.6) of amorphous alloy ribbons were finally prepared by melt spinning of single roll casting method. The obtained ribbon alloy ribbons have the thickness in about25μm, width in about2mm.we used lots of testing tools, such as X-ray diffraction (XRD), Transmission electron microscopy (TEM), Mossbauer spectroscopy (MS) to confirming that thin tape quenched alloy is complete amorphous. The X-ray diffraction patterns show a diffuse diffraction peak, the pictures of transmission electrical microscopy show that diffraction rings are disperse cyclic structure, and the pattern of the matrix is homogeneous, Mossbauer spectrum analysis indicate the as-quenched alloy presents a typical broadened and overlapped sextet, and the second and fifth peaks are higher than the first and the sixth peaks obviously. These all confirm that thin tape quenched alloys are complete amorphous.The amorphous thin ribbons were treated by middle-frequency magnetic pulsing. The parameters of pulsed magnetic field are intensity of magnetic field from1000e to2500e, pulse frequency from500Hz to2000Hz, pulse time from5min to20min. Middle-frequency magnetic pulsing treatment can achieve amorphous alloys single-phase nanocrystallization. During the crystallization processes, the nanocrystalline phase α-Fe(Co) is born and dispersed in the residual amorphous matrix phase to form the so-called two-phase nanocrystalline alloys. After being treated under the middle-frequency magnetic pulse treatment conditions, the activation energy of nanocrystalline alloys are slightly higher than the value of the quenched alloy.We use fast-fast coincidence ORTEC system to measure PAS. In order to acquire positron annihilation lifetime τi and the corresponding annihilation intensity Ii(i=l,2,3), we use three-exponent damped components to free fitting PAS. Among them τ1correspond with the single vacancy (or simple single vacancy) PAS, τ2correspond with the vacancy group PAS, τ3correspond with the PAS of source surface, inner surface of samples or within the space between the source and samples. The results indicate that after being treated under the different treatment conditions, each kind of the positron annihilation lifetime value τi of alloys exhibits decline trends. And the each kind of lifetime component corresponding to the strength Ii also appears smaller amplitude fluctuations.