Temperature dependence of fracture toughness in cleavage fracture of iron and iron alloys

In order to examine the temperature dependence of fracture toughness in cleavage fracture, exploratory work was carried out. Then effects of alloying elements and micro-structure on the low temperature fracture toughness were studied quantitatively in iron and iron alloys.The results indicate that (1) the relationship between fracture toughness G_ic and testing temperature T at low temperatures is G_ic = G_o exp (T/T_e), where G_e and T_o are the material constants; (2) G_o exhibits a stro dependence on solute carbon and nitrogen contents but is independent of micro-structure and other elements; (3) G_o values increases with increasing solute carbon and nitrogen contents; (4) T_o depends on the structure; (5) $\text{1}\text{T}{}_{\mathrm{o}}$ values increase with increasing nickel and manganese contents, to the contrary, decrease with increasing carbon, silicon and phosphorus contents; and (6) $\text{1}\text{T}{}_{\mathrm{o}}$ values increase with decreasing grain size.