“…Lower T Q would increase the yield strength by larger fraction of martensite which is the strongest microstructure, while higher T P could induce an active formation of Cottrell atmosphere where dislocation is pinned by solute carbon, which was often found in the tempering of martensite and known to increase yield strength. 29,30) It is noted that the yield strength exhibits nearly constant with the silicon content except for the Q250 P350 condition where the yield strength is gradually decreased with the silicon content. It seems to contradict the general practice that silicon is one of the effective solid solution hardening elements.…”