Amorphous microwires of Fe73.8Si13B9.1Cu1Nb3.1 and Fe77.5Si13.5B9 composition fabricated by the Ulitovsky–Taylor method were studied. The samples with the glass shell removed were heated at temperatures of 753 K and 703 K for 20 minutes, afterwards, their structure was examined using X-ray diffraction. Subsequently, the thermally treated samples were chemically etched and X-ray diffraction study of the structure was again carried out. Experimental results on the predominant crystallization of near-surface regions were discussed assuming that mechanical stresses affect the nucleation and growth of nanocrystals.