Electric guitar strings E6, A5 and D4 consist of two parts: steel
core with thin layer of Sn, thickness is about 1 mm (Fig. 1A and B)
and steel wrap with Ni coating. Shape of cross-section of E6, A5
and D4 strings is same and essential difference is only in
diameter of strings. Diameter of E6, A5 and D4 strings is 1.07,
0.81 and 0.61 mm, respectively. The microstructure of wrap of E6
string includes typical ferrite crystals of low carbon steel (Fig. 1D).
Same microstructure have wrap A5 and D4 (not shown here).
Generally, results of microstructure (Fig. 1D) as well as chemica