Nanocomposites and nanomaterials
Effect of Constant Magnetic Field on the Properties of Amorphous Alloys based on Transition Metals                   

Tsaregradskaya T.L., Ovsiienko I.V., Kozachenko V.V, Kurilyik A.M., Saenko G.V., Kalenyk O.O., Turkov O.V.
Taras Shevchenko National University of Kyiv, Department of Physics
01601, Volodymyrska st. 64/13, Kyiv, Ukraine
E-mail: tsar_grd@ukr.net

The magnetic field is one of the thermodynamic factors that effect the kinetics and mechanisms of structural-phase changes in various materials and create an effective opportunity to influence the structure and, consequently, the functional properties of materials. It is established that the micromechanical properties of amorphous alloys Co67Fe3Cr3Si15B12 and Ni40Fe40B20, the indicator of which is microhardness, under the influence of a magnetic field of 0.64 T undergo the following changes: at the initial stages of the experiment up to (15-25) days there is a decrease in microhardness (22-27%) ie increasing the ductility) of alloys, and with increasing the time of exposure to the magnetic field to (50-100) days there is a gradual strengthening and reduction of microhardness is (13-18)%.
It is shown that the thermal stability of amorphous alloys after treatment in a magnetic field increases: for Co67Fe3Cr3Si15B12 alloy the increase in thermal stability is maximum after treatment for 15 days and is 70 K, with further increase in processing time the effect decreases and after treatment for 50 days stabilizes at 40 K; for Ni40Fe40B20alloy, the increase in thermal stability is maximum after treatment for 25 days and is 50 K, with a further increase in exposure time, the effect decreases and after treatment for 50 days stabilizes and is 30 K. 
The nonmonotonic dependence of the relative change in microhardness and thermal stability of amorphous alloys on the time of exposure to the magnetic field is explained by the fact that magnetic treatment causes two competing processes that cause changes in these parameters: fast acting - decay of clusters (borides and silicides) and  long-term - the growth of frozen crystallization centers, which leads to the strengthening of the structure, which causes a decrease in the magnetoplastic effect and the effect of increasing thermal stability. 
This fact was confirmed by studies of the amorphous alloy surface morphology carried out using the atomic force microscope (AFM) NT-MDT NTEGRA Prima Scanning Probe Microscope in the non-contact mode.