The treatment schemes consisted in first heating the material to a temperature above Ac1, and then either cooling it very slowly in a furnace (schemes no. 1 and 5) or maintaining it at a temperature just below Ar1 (schemes no. 4 and 7), or prolonged holding of the material at the Ac1 temperature (schemes no. 2 and 3) followed by alternate heating and cooling of the material at temperatures that are just below Ar1 and just above Ac1.