Effects of addition of yttrium on properties and microstructure for China Low Activation Martensitic (CLAM) steel

The effects of yttrium on properties and microstructure for China Low Activation Martensitic (CLAM) steel have been investigated. The tensile test shows that the addition of 0.2% yttrium decreases the strength of CLAM steel before irradiation. The results obtained by positron annihilation lifetime measurements of the CLAM, F82H and T91 steels irradiated by 80 MeV 19F ions to 10 dpa demonstrate that the irradiation resistant property of CLAM steel with yttrium is much better than that of other two steels. The SEM and TEM observations suggest the addition of yttrium both refines the martensitic lath structure and leads to the precipitation of big Y2Fe17C0.75 compound.