HEAVY ION IMPLANTATION INDUCED MARTENSITIC TRANSFORMATIONS IN NICKEL AND STAINLESS STEEL

Abstract
Recent investigations have shown that ion implantation of metals at room temperature may induce diffusionless transformations resulting in either martensite formation or in amorphization. Rutherford backscattering analysis and transmission electron microscopy/diffraction have been used to investigate nickel and 316 stainless steel crystals implanted with 80 keV Sb⁺ ions to fluences of 5.10²⁰ m^-2. The resulting microstructure consists, beside dislocation tangles, of distributions of new phase particles 0.1- 0.2 µm in size. Hcp particles with the Shoji-Nishiyama orientation relationship are formed in nickel, while stainless steel shows formation of bcc particles with the Nishiyama-Wassermann orientation relationship, both of which being well known from the field of martensitic transformations. RBS analysis shows that the antimony in nickel is incorporated substitutionally in the lattice even at concentrations ˜ 20 at.%, while the antimony in stainless steel is distributed randomly throughout the implantation zone. In both materials the martensite particles are believed to form as a result of large stress concentrations, induced during implantation.