What are the effects of alloy elements on the mechanical properties of ASTM A709 bridge steel plate

What are the effects of alloy elements on the mechanical properties of ASTM A709 bridge steel plate?

Effect of alloy elements on mechanical properties of ASTM A709 bridge steel plate in annealed state:
The basic phase of ASTM A709 bridge steel plate in annealed state is ferrite and carbide. The alloy element dissolves in the ferrite to form the alloy ferrite, which can improve the strength and hardness of ASTM A709 bridge steel plate, but reduce the plasticity and toughness at the same time.

Effect of alloy elements on mechanical properties of ASTM A709 bridge steel plate in quenching and tempering state:
The strengthening effect of alloy element on ASTM A709 bridge steel plate in quenching and tempering state is very significant, because it makes full use of all four strengthening mechanisms. Martensite is formed during quenching and carbide is precipitated during tempering, which results in strong second phase strengthening and greatly improves toughness. Therefore, it is an economic and effective comprehensive strengthening method to obtain martensite and temper it.