Cu添加マルテンサイト超高強度鋼における析出硬化挙動と機械的性質(力学特性)

概要

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Cu precipitation hardening behavior and mechanical properties were investigated in Cu added martensitic ultra-high strength steels. In this work, hardness measurement, TEM observation, lattice parameter measurement and tensile testing were conducted for 0.19%C-1.5%Mn steels with addition of up to 4% Cu those were water-quenched followed by aging at 250 through 550℃ for 20s through 360min. Cu added steels exhibited higher hardness than a Cu free steel in each aging condition. Precipitated Cu content estimated by lattice parameter well corresponded to hardness increment in 4% Cu steels compared with Cu free steels aged at the same aging condition. Regarding the tensile properties of the aged Cu free and 4% Cu steels, 4% Cu steel exhibited superior balance of tensile strength and elongation with tensile strength level of 1300MPa. Lower activation energy estimated by peak hardness increment than that of Cu diffusion in bcc-Fe matrix suggested that high dislocation density introduced by martensitic transformation accelerated the growth of Cu precipitates. And smaller Cu precipitation hardening in martensite matrix compared with that in ferrite matrix was also discussed taking into consideration nonlinear summation of dislocation hardening and precipitation hardening.
社団法人日本鉄鋼協会の論文
2008-11-01