Effect of solute copper on hardness and ductile-to-brittle transition in alpha-iron

Effects of solute Cu on strengthening and ductile-to-brittle transition (DB T) of alpha-iron have studied for Fe-(0 similar to 2)mass%Cu alloys, The Fe -Cu alloys exhibit massive ferritic transformation on water-quenching from solution treatment temperature, With increasing Cu content, the massive fer rite grains were refined and the hardness was raised. Effect of the solid s olution hardening is predominant to the strengthening, but the refinement o f massive ferrite grains does not affect so much. Charpy impact tests showe d that Cu addition substantially lowers DBT temperature of alpha-iron. The embrittleness at low temperature was caused by the onset of cleavage cracks tit ferrite grain boundaries where deformation twins impinged. Copper in s olution suppresses the formation of deformation twins, and this results in the shift of DBT temperature to lower side.