Cu-Ni-Sn 합금의 상변태거동 및 기계적 성질에 미치는 Mn 첨가효과

The effects of Mn addition on phase transformation behavior and mechanical properties of Cu-(9-x)Ni-xMn-6Sn alloys were investigated. The microstructure and transformation behavior changed with increasing Mn content and heating temperature. The Mn free alloy decomposed spinodally by aging at 350℃ and followed by formation of a metastable γ′ phase which accompanies the increase of mechanical characteristics with increasing Mn content, however, the γ′ phase disappeared and a stable γ phase was dominantly precipitated. When the specimens were aged above 450℃, equilibrium γ phase formed from the initial stage of transformation without any reaction such as spinodal decomposition and transformation of a metastable phase. Therefore, addition of Mn and increasing heating temperature suppressed the hardening effect of alloy in the early stage of aging, and decreased the tensile strength.