材料期刊网

Plastic strain range (3 x 10(-3)-1.2 x 10(-2)) controlled low cycle fatigue (LCF) tests have been performed using an annealed polycrystalline alpha-Fe with and without metallic ion implantations. Ag+, Cr+, Y+, and Al+ ion implantation was carried out at an energy range of 90-120 keV and a dose of 5 X 10(16) ions/cm(2). It was found that the fatigue resistance of alpha-Fe was increased, and the fatigue crack initiation (FCI) life extended by implantation. The cyclic stress-strain (CSS) plots revealed that the as-implanted specimens experienced a cyclic softening (saturation stress decrease) compared with the unimplanted specimens. Surface plastic strain homogenisations were observed for the implanted specimens. An implantation induced enhancement of screw dislocation annihilations by cross slip instead of causing the formation of a kink pairs mechanism was proposed to correlate the strain homogenisation with the relative cyclic softening, and thus to explain the improved LCF property of alpha-Fe by implantation.